T cell activation and signal transduction

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

Src Kinases

Src family kinases are named after the transforming gene of Rous sarcoma virus, the first animal tumor virus identified.

Src (pronounced "sarc" as it is short for sarcoma) is a family of proto-oncogenic tyrosine kinases discovered by J. Michael Bishop and Harold Varmus, for which they won the 1989 Nobel Prize. The discovery of Src family proteins has been instrumental to the understanding of cancer as a disease where normally healthy cellular signalling has gone awry.

The Src family includes 9 members:

SrcA subfamily
- Src
- Yes
- Fyn
- Fgr

SrcB subfamily
- Lck
- Hck
- Blk
- Lyn

Frk is in its own subfamily

Phosphorylation events in T cell activation:

Lck (Src kinases Lyn, Fyn, Blk in B cells)
ZAP (Syk in B cells)

PLC
LAT (SLP/Btk in B cells)
Grb2

SOS
RAS, MAPK

NAN (NFAT, AP-1, NFkB)

C-src tyrosine kinase

C-src tyrosine kinase, also known as CSK, includes an SH2 domain, an SH3 domain, and a tyrosine kinase domain. C-src also acts on the LYN and FYN kinases.

LYN

LYN is V-yes-1 Yamaguchi sarcoma viral related oncogene homolog. LYN is a member of the Src family of protein tyrosine kinases, which is mainly expressed in hematopoietic cells and in neural tissues. LYN is associated with cell surface receptor proteins, including the B cell antigen receptor (BCR), CD40, or CD19.

Lck

Lck (or leukocyte-specific protein tyrosine kinase) is a protein that is found inside lymphocytes. Lck is a member of the Src family of tyrosine kinases.

SYK

SYK (Spleen tyrosine kinase) is an enyzme encoded by the SYK gene. SYK and ZAP-70 are members of the Syk family of tyrosine kinases. Please make a distinction between the Src family of tyrosine kinases (9 members, listed above) and the Syk family of tyrosine kinases (SYK and ZAP-70).

Within B and T cells respectively, SYK and ZAP-70 transmit signals from the B-Cell receptor and T-Cell receptor.

B-cells have SYK
T-cells have ZAP

LAT

LAT (Linker of Activated T cells) is a protein phosphorylated by ZAP70/SYK protein tyrosine kinases following activation of the T-cell antigen receptor (TCR) signal transduction pathway.

B cell activation and signal transduction (click on the little for full text)

Phosphorylation events in B cell activation:

Src kinases Lyn, Fyn, Blk
Syk

PLC
SLP/Btk
Grb2

SOS
RAS, MAPK

NAN (NFAT, AP-1, NFkB)

Complement receptor CD21 (CR2) activates BCR if the antigen is opsonized by C3b component of the complement.

CR2-CD19-CD81 complex is expressed on the surface of B lymphocytes.

Activation of B cells depends on the following:

- CD 19 and CD21 (CR2)
- TAPA 1
- CD81
- ITAM (universal activation motif)

Inhibition of B cells depends on the following:

- CD22
- CD45
- FcγRIIb (CD32)
- CTLA-4 (Cytotoxic T-lymphocyte antigen-4)
- ITIM (universal inhibition motif)


T and B Cells - Naive and Memory Cell Markers (click to enlarge the image).

T cell activation involves all of the following steps EXCEPT:

A. RAS-MAPK pathway

B. activation of Syk

C. activation of NFAT

D. activation of Protein Kinase C

Answer: B. Syk is part of the B cell activation. ZAP-70 is its equivalent in T cells.

References

Src (gene). Wikipedia.
LYN. Wikipedia.
Lck. Wikipedia.
SYK. Wikipedia.
LAT, Linker of activated T cells. Wikipedia.

Related reading

Redirecting T Cells - NEJM, 2011.
Genomics and the Multifactorial Nature of Human Autoimmune Disease. NEJM, 2011.

Published: 08/29/2009
Updated: 09/29/2011

Co-stimulators and their ligands on antigen presenting cells and T cells

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

There is no T cell response without costimulation. If T cells recognize the antigen but are not co-stimulated, they go in a state of anergy or nonresponsiveness.

Two co-stimulators produce negative response instead of positive response (activation). The negative co-stimulators are CTLA-4 and PD-1 on T cells. They are connected to ITIMs.

Pairs of co-stimulators and their ligands:

Left - antigen presenting cells (APC) -- right - T cells

CD 80 (B7-1 in mouse) -- CD 28
CD 86 (B7-2 in mouse) -- CTLA-4 (negative response)
ICOS-L -- ICOS (class switch)
OX40L -- OX40
CD40 -- CD40L (class switch)
PD-L1/PD-L2 -- PD-1 (negative response, PD - Programmed Death)

Abbreviations: ITIM, immunoreceptor tyrosine inhibitory motifs; ICOS, inducible co-stimulator; PD-1, programmed death.

CD152 is cytotoxic T-lymphocyte antigen-4 (CTLA-4). CTLA-4 binds to CD80 and CD86 receptors with a higher affinity than CD28, and inhibits T cell activation.

Abatacept (Orencia) is CTLA4-human IgG1 fusion protein against B7-1 (CD80) and B7-2 (CD86). It is used for treatment of rheumatoid arthritis and juvenile rheumatoid arthritis.

Published: 05/12/2010
Updated: 09/22/2010

Reactions to multiple foods due to oral allergy syndrome rather than food allergy

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

A 31-year-old Caucasian male is here for evaluation of reported allergies to multiple foods. He had allergy symptoms after eating soy and almonds as a child and he has avoided them ever since. He reports increasing reactions to multiple foods during the last 3-4 years, especially in the last 6 months. The reactions consist mostly of oral itching and "unusual sensation" inside his mouth almost immediately after consuming a wide range of foods including apple, peach, apricot, hazelnut, carrot, banana, cucumber, watermelon and zucchini. He has no issues whatsoever when he consumes the same food in a cooked form. He does not report any wheezing, shortness of breath, abdominal pain or any other systemic symptoms when he consumes those foods and no urticaria either. He has a history of allergic rhinitis with multiple sensitizations to different types of allergens and he had received immunotherapy for less than 2 years, approximately 4-5 years ago. He remembers that skin prick tests were positive for cat, dust mites and dog. He is very active, and rides a bicycle regularly without any respiratory symptoms.

Past medical history (PMH)

Allergic rhinitis, received immunotherapy for less than 2 years, approximately 4-5 years ago.

Medications

None.

Social history and family history

Unremarkable.

Physical Examination

HEENT exam showed pale boggy turbinates on both sides. The rest of the physical examination was unremarkable.

What is the most likely diagnosis?

- Oral allergy syndrome
- Food allergy

What tests would you suggest?

- Skin prick testing
- ImmunoCAP for specific IgEs

What happened?

The skin prick testing result was quite remarkable with large positive reactions to multiple aeroallergens and in fact, those reactions were larger than the histamine reaction. The positive reactions were to cat, dust mite, tree mix, birch mix, grass mix, Timothy grass, rye grass, ragweed mix, and weed mix.

This is a patient with allergic rhinitis with multiple sensitizations to different types of allergens and cross reactivity when consuming certain foods, which is typical of the diagnosis of oral allergy syndrome. There is a known cross reactivity in patients who are sensitized to birch, when they consume apple, peach, apricot, hazelnut, potato, and celery in raw form. There is a known cross reactivity in patients who are sensitized to ragweed who consume banana, cantaloupe, watermelon, zucchini and cucumber. Our patient is sensitized to both birch and ragweed. Also, he is sensitized to weed mix as well, which confers additional and different cross reactivity. It is typical for oral allergy syndrome that the patients react when they consume raw foods, but not cooked foods.

What treatment would you recommend?

The patient was advised to avoid the use of raw vegetables which trigger symptoms. There is a slight risk of systemic reaction which in the range of 1% to 10% in patients who have oral allergy syndrome when they consume the offending foods in raw form. He was advised to have an Epi-Pen at all times if a systemic reaction develops. We also recommended that he should take an oral antihistamine consisting of cetirizine 10 mg daily, and Singulair 10 mg p.o. daily. The treatment with antihistamine may alleviate some of his local reactions when he consumes the triggering foods. He has significant allergic rhinitis and we recommended a steroid nose spray to be used twice a day. We also ordered specific IgE blood testing to almonds, soy, walnut, apple and potato to check the levels of the specific IgE to foods that triggered more significant reactions in the past.

Final diagnosis

Oral allergy syndrome.

References

Profilin may be a pan-allergen among plants that crossreacts between pollen, fruits, vegetables and latex http://goo.gl/ZUPRQ

Cross Reactions Among Foods (PDF).

Related reading

Flavored Coffee May Trigger Seasonal Allergies - due to oral allergy syndrome. Fox News, 2011.
Oral symptoms from the ingestion of food in a patient with allergic rhinitis - AAAAI Ask the Expert, 2011.
In birch-apple syndrome (oral allergy syndrome), eating apple does not affect the respiratory tract. Annals of Allergy, Asthma and Immunology, 2011.

Published: 07/03/2010
Updated: 12/12/2011

Vocal Cord Dysfunction in an Athlete with Asthma

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

A 17-year-old Caucasian female has been referred for respiratory problems during exercise. She was diagnosed with asthma in early childhood and has been receiving treatment with Singulair, Maxair and Advair. She feels that during the last 5 years her asthma has gotten worse, especially in the last year. The symptoms are more pronounced when she exercises. Some of her reported symptoms extend beyond the scope of a typical asthma attack, for example, she reports trouble getting air in rather than out, changes in her voice, even losing her voice to the extend that she cannot speak. The symptoms are mostly when she exercises and they are not relieved by the use of a short-acting bronchodilator, Maxair inhaler. She reports symptoms of trouble getting air in and changing her voice also with strong emotions or anxiety, but she does not have history of typical anxiety attacks. She does have nasal congestion. She has been treated with prednisone bursts 4-5 times in the past year. No emergency room visits or hospitalizations. She reports slight relief in her symptoms with the prednisone, but not complete relief. She does use albuterol 30 minutes before exercise, but does not feel that this prevents her symptoms and there is no evidence of improvement with Advair, which has been started in the past year. She is an active athlete and she runs track.

Past medical history (PMH)

Asthma, allergic rhinitis.

Medications

Singulair 10 mg p.o. q h.s., Advair 100/50 one inhalation b.i.d., Maxair as needed.

Social history and family history

Allergic rhinitis in her mother.

Physical Examination

HEENT exam showed pale boggy turbinates on both sides. The rest of the physical examination was unremarkable.

What is the most likely diagnosis?

- Vocal cord dysfunction
- Exercise-induced bronchospasm

What tests would you suggest?

- Baseline spirometry
- Exercise challenge with pre- and post-test spirometry
- Laryngoscopy

Procedures done today included a spirometry, which showed FVC of 81%, and FEV1 of 91%. However, she had trouble achieving the peak of the flow volume loop and there was early stop of the expiration. The specifics of the maneuver showed some features of vocal cord dysfunction during the performance.

What happened next?

This is a patient with predominantly exercise-induced respiratory symptoms. The full explanation of the symptoms can be provided by the diagnosis of asthma and/or exercise-induced bronchospasm. From the history, examination and the spirometry, there is some evidence that vocal cord dysfunction plays a significant role in her symptoms.

Vocal cord dysfunction is exemplified by the patient having trouble inhaling rather than exhaling air and voice changes during the attack. Also, the fact that her symptoms are not alleviated by inhaled bronchodilator makes the diagnosis of vocal cord dysfunction more likely. She does have evidence of allergic rhinitis on physical examination, but the patient declined skin prick testing at this time and will consider it at a later time.

The current treatment with Singulair and Advair was continued. The inhaler technique and administration was reviewed and it was correct. A laryngoscopy evaluation by ENT for vocal cord dysfunction was arranged. A nose spray was prescribed, Nasonex 1 spray in each nostril b.i.d.

Final diagnosis

Vocal cord dysfunction in an athlete.

References

Video: Expiratory Vocal Cord Dysfunction and Laryngopharyngeal Reflux. CityAllergy: 62 yr old woman w/spasmodic coughing, wheezing and chronic dyspnea. Her PFTs showed a barely obstructive contour and she did not improve with inhaled or oral steroids. Her endoscopy showed evidence of LPR and posterior kinking of the larynx with expiration (classic VCD has inspiratory kinking).

Vocal Cord Dysfunction: Differential Diagnoses & Workup. eMedicine Specialties > Allergy and Immunology > Asthma.

Paradoxical Vocal-Cord Dysfunction: Management in Athletes. J Athl Train. 2002 Jul–Sep; 37(3): 325–328.

Vocal Cord Dysfunction: Paradoxical Vocal Cord Motion. Grand Rounds Presentation, UTMB, Dept. of Otolaryngology, 2001.

Vocal cord dysfunction (VCD) masquerading as "asthma" for 20 years

Use of videography in the diagnosis of exercise-induced vocal cord dysfunction: A case report with video clips. JACI, Volume 119, Issue 6, Pages 1329-1331 (June 2007)

Related reading

Olympic athlete hopeful improves her symptoms - and running time - after vocal training for vocal cord dysfunction. Daily Mail, 2011.

Published: 07/03/2010

Updated: 02/12/2011

Wheat Allergy

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

Wheat is one of the major crops grown and consumed by humankind and is associated with both intolerances (notably coeliac disease) and allergies.

Three types of allergy are particularly well characterized

- Food allergy to wheat. Some new allergens, including nonspecific lipid transfer protein (Tri a 14), have been identified.

- Wheat-dependent exercise-induced anaphylaxis (WDEIA), with the omega(5)-gliadins (part of the gluten protein fraction) being the major group of proteins which are responsible. Wheat is the most common food associated with food-dependent exercise-induced anaphylaxis.

- Bakers' asthma - results from the inhalation of flour and dust during grain processing.

Celiac disease is different from wheat allergy

Celiac disease is not a wheat allergy or gluten allergy. Celiac disease is an autoimmune disease triggered by eating gluten. Patients with celiac disease will not lose their sensitivity to gluten. Celiac disease requires a lifelong restriction of gluten.

The major grains that contain gluten are wheat, rye, and barley. These grains must be strictly avoided by patients with celiac disease.

Wheat-allergic people have an IgE-mediated response to wheat protein. These individuals must only avoid wheat. Most wheat-allergic children will outgrow the allergy.

What is the cross-reactivity risk between wheat and other grains?

Twenty percent (20%).

Diagnosis of wheat allergy

Wheat allergy is rare in adults bit it can occur. In adults, specific IgE was more sensitive than skin test for wheat; however, specificity and predictive values were low for both tests. Thus, these tests should not be used to validate diagnosis of wheat allergy. An oral challenge should be performed to confirm or exclude the diagnosis of wheat allergy.

As with skin prick testing for inhalant allergens, wheal size has diagnostic value for many food allergens. In a study that evaluated subjects with a history of peanut allergy by skin-prick tests, antigen-specific IgE assays, and challenges, the positive predictive value for a clinical allergy was 94.4% for a wheal diameter of at least 8 mm, with a specificity of 98.5%.

However, this does not apply to all allergens. For example, skin test results as well as antigen-specific IgE values should not be used to validate a diagnosis of wheat allergy because their specificity and predictive values are much lower.

Skin tests with commercial food allergen extracts are much less reliable than skin tests with inhalant allergens, and only a fraction of patients with positive food skin tests will react during a food challenge. Many patients having IgE antibodies to foods either do not react or have lost their clinical sensitivities.

With food extracts, prick-puncture tests ("prick-prick") seem to be more reliable.

Prognosis

In children, 85% of cow’s milk, egg, wheat, and soy allergy resolves by five years. In contrast, only 20% of children “outgrow” their peanut allergy, and only 9% of tree nut-allergic patients do so.

Food challenge

There is a strong correlation between the level of specific IgE and the need for medical intervention - the high-risk cut-offs are 17.5 kU/L for milk, wheat, and soy, and 3.5 kU/L for egg. Researchers recommended establishing intravenous access in children with specific IgE levels of 17.5 kU/L to milk or wheat or 3.5 kU/L to egg.

There are predetermined levels of specific IgE on ImmunoCAP below which a food challenge can be attempted. Those levels are shown in the grid below:


Levels of specific IgE below which a food challenge can be attempted. Image source: Dr. Hopp, Creighton University Division of Allergy & Immunology, used with permission.

These are proposed starting doses for oral challenges: peanut 0.1 mg, milk 0.1 mL, egg 1 mg, wheat 100 mg, soy 1 mg, cod 5 mg, shrimp 5 mg, and hazelnut 0.1 mg


8 top allergens account for 90 percent of food allergies. Specific IgE levels (sIgE) that predict the likelihood of passing an oral food challenge are shown in the figure. (click to enlarge the image).

References

Adkinson: Middleton's Allergy: Principles and Practice, 7th ed.
Allergens to wheat and related cereals. Tatham AS, Shewry PR. Clin Exp Allergy. 2008 Nov;38(11):1712-26. Epub 2008 Sep 24.
Food Allergies: Detection and Management. Am Fam Physician. 2008 Jun 15;77(12):1678-1686.
Wheat allergy. Inomata N. Curr Opin Allergy Clin Immunol. 2009 Jun;9(3):238-43.
Wheat allergy: a double-blind, placebo-controlled study in adults. Scibilia J, Pastorello EA, Zisa G, Ottolenghi A, Bindslev-Jensen C, Pravettoni V, Scovena E, Robino A, Ortolani C. J Allergy Clin Immunol. 2006 Feb;117(2):433-9.
Wheat Allergy. FoodAllergy.org.

Food-dependent exercise-induced anaphylaxis (FDEIA)

Food Challenges for Diagnosis of Food Allergy

Nonceliac gluten-sensitive enteropathy (NCGSE) common in allergic patients - biopsy part of the routine investigation? http://goo.gl/gwdT3

Cross Reactions Among Foods (PDF).
Celiac Disease - JAMA Patient Page (PDF)



ClevelandClinic, October 11, 2010: Celiac disease is when the body doesn't tolerate gluten very well - the protein found in wheat, barley and rye. When people with celiac disease eat gluten it damages the small instestines. Symptoms are gas, bloating, indigestion, fatigue, and headaches. This disease is diagnosed by a blood test.

Published: 07/28/2010
Updated: 02/16/2011

Pruritus secondary to opioids without evidence of allergic reaction after a graded drug challenge with oxycodone

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

A 24-year-old Caucasian female with a history of recurrent back pain and several back surgeries is referred for symptoms of urticaria and pruritus secondary to multiple pain medications during the last 3 to 4 years. She reports reactions to morphine, codeine, oxycodone, Topamax, Ultram, Celebrex and sulfa. In all cases hives occur soon after taking the medication and they never last more than 24 hours. The hives disappear after taking an antihistamine. She also has a history of panic attacks. During those episodes on a few occasions she had hives and had trouble breathing, but no real episodes of throat closing, low blood pressure, abdominal or respiratory symptoms during the episodes of urticaria with taking opioids.

Past medical history (PMH)

Recurrent back pain and several back surgeries, urticaria and pruritus secondary to multiple medications.

Medications

Elavil, Lexapro, ibuprofen p.r.n.

Social history and family history

Unremarkable.

Physical Examination

Normal.

What is the most likely diagnosis?

This is a patient with evidence of intolerance to opioids manifested by histamine release and acute urticarial episodes which typically resolve with or without antihistamines within 24 hours. There is no evidence of allergic or pseudoallergic reaction. There is no evidence of anaphylaxis or life-threatening reactions to opioids.

What tests would you suggest?

Graded drug challenge with oxycodone (short-acting opioid).

Table 1. Graded drug challenge with oxycodone

Q 15 minutes

0.078125 mg

0.15625 mg

0.3125 mg

0.625 mg

1.25 mg

2.5 mg

5 mg = full capsule

What happened next?

There was a suspicion that she may be allergic to opioids and several other medications as listed above. However, this is unlikely with her history - pruritus induced by opioid medications is quite common, and it occurs in about 12% to 15% of patients taking opioids. It is mediated both by peripheral release of histamine by the mast cells in the skin and also by central effect via the mu receptors. Antihistamines are not particularly effective, but they are worth a therapeutic trial, and that was done in this patient.

The patient returned for graded drug challenge 10 days after the initial visit. The current medications included Zyrtec 10 mg p.o. daily and she came with a prescription of oxycodone 5 mg capsules to be taken 4 to 6 times a day p.r.n. pain.

She had been on Zyrtec 10 mg p.o. daily for the last 4 days. We performed a graded drug challenge, starting with a dose of 0.078 mg of oxycodone dissolved in water. The patient was able to tolerate that. After the first and second dose of the medication, she developed pruritus affecting her extremities, face, the back of the head and the abdomen, but no hives, and no other changes in her physical condition.

She was able to tolerate up to 5 mg of oxycodone (total dose) in increments according to the drug challenge protocol. She had pruritus which worsened and improved spontaneously. With the dose of 1.25 mg of oxycodone, we gave her cetirizine 10 mg p.o. x1 in addition to the dose she had taken in the morning, and she reported no improvement in the pruritus with that.

Approximately 2 hours after the first dose of oxycodone, we provided a second dose of 5 mg of oxycodone, and the patient continued to have pruritus, but her blood pressure was stable, and there were no other symptoms. However, she reported feeling somnolent and dizzy, and she was advised to have lunch, which she did, with some improvement. There was no significant change in the blood pressure or other vital signs.

In summary, this is a patient with intolerance to oxycodone manifested by pruritus and feelings of dizziness and somnolence which again are quite common, with somnolence occurring between 23% to 24% of patients in general, dizziness 13% to 16%, and pruritus in 12% to 13%. She did not have hypotension, nausea, or vomiting. She stayed at the clinic for 2 hours after the challenge to recover from the somnolence, but there were no allergic symptoms.

Summary

The pruritus secondary to opioids experienced by this patient is most likely centrally mediated and antihistamines may be of limited effect. From an allergy and immunology perspective, there is no evidence of allergy to opioid medications, and there is no contraindication to starting methadone at this point as recommended by the pain management specialist. However, considering that she has reactions in terms of somnolence, dizziness and headache, it is probably best to give her the first dose at the physician's office and also start with a low dose of the opioid pain medication.

Final diagnosis

Pruritus secondary to opioids without evidence of allergic reaction after a graded drug challenge with oxycodone.

References

To be updated.

Published: 07/03/2010
Updated: 08/03/2010

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