Allergy and Immunology

Question 1

Which part of the immune system is rapid and nonspecific?

Answer 1

The innate immune system is rapid and nonspecific. This includes the skin, complement, macrophages,and natural killer cells.

Question 2

Which part of the immune system is slow and specific?

Answer 2

The adaptive immune system is slow and specific. It can be divided into the humoral immune system consisting of B-cells, plasma cells, and Igs and the cellular immune system consisting of T-cells, activated macrophages, and activated NK cells.

Question 3

What is MHC restriction?

Answer 3

MHC restriction is the concept that T-cells can only recognize antigens if they are presented by HLA. CD4 cells are activated by antigens presented by class 2 HLA. CD8 cells are activaed by antigens presented by class 1 HLA.

Question 4

What are class I HLAs? Where are they located?

Answer 4

Class 1 HLAs (HLA-A, -B, and -C) are located on all nucleated cells. They present antigen to CD8 cells and play a role in transplant rejection, neoplasms, and infections.

Question 5

What are class II HLAs? Where are they located?

Answer 5

Class 2 HLAs (HLA-DP, -DQ, and -DR) are present on antigen presenting cells such as monocytes/macrophages, Langerhans cells, dendritic cells, and B-cells. CD4 cells only recognize antigens presented with class 2 HLA.

Question 6

What functions are the same and what are different in CD4+ and CD8+ cells?

Answer 6

CD4 cells are the primary defence against extracellular threats. CD8 cells are cytotoxic and important in defence against intracellular threats such as viruses and neoplasms.

Question 7

What is the important distinction between the way NK cells and NKT cells kill other cells?

Answer 7

Unlike NK cells, NKT cells have T-cell receptors and require a signal to kill.

Question 8

Which immunoglobulins are present on the surface of mature B cells?

Answer 8

Mature B cells have IgM and IgD on their surfaces.

Question 9

Characterize the various immunoglobulins: G, A, M, E and D.

Answer 9

IgG is the main Ig in serum. It is commonly elevated in chronic infections. It crosses the placenta and activates complement.
IgA is the main Ig in secretions. It is secreted in milk. It does not activate complement.
IgM is the first Ig produced in an infection. It is a monomer on the cell surface but secreted as a pentamer. It is a potnet activator of complement.
IgE is a major factor in allergic conditions including asthma, allergic rhinitis, atopoic dermatitis, and food allergies.
IgD is found in trace amounts and has an unknown function.

Question 10

Which antibody crosses the placenta?

Answer 10

IgG crosses the placenta.

Question 11

Which antibody is secreted first during an infection?

Answer 11

IgM is secreted first in an infection.

Question 12

What is the cause of hereditary angioedema? What is the clinical presentation?

Answer 12

Hereditary angioedema is caused by deficiency of C1 inhibitor.

Question 13

Which infection is most often seen with terminal complement deficiency?

Answer 13

Deficiency of terminal complement results in increased Neisseria infections (meningococcal and gonococcal).

Question 14

What does the CH50 assay measure, and when is it used?

Answer 14

CH50 measures the total complement hemolytic activity of the classical pathway. The CH50 is a good screen for complement deficiencies. If the CH50 is very low, check the individual complement levels.

Question 15

What mediates immediate hypersensitivity reactions?

.

Answer 15

Type 1 hypersensitivity reactions are mediated by IgE and most of the acute symptoms are due to histamine release

Question 16

When does the late phase of a Type 1 hypersensitivity reaction occur? Why does it occur?

Answer 16

The late phase response in type 1 hypersensitivity occurs 3-12 hours after the acute response in >25% of cases. The initial IgE reaction stimulates synthesis of cytokines and the subsequent cellular recruitment of eosinophils and basophils. This results in an eosinophilic inflammatory infiltrate.

Question 17

What is the treatment for anaphylaxis?

Answer 17

The initial treatment of anaphylaxis is 0.2-0.5cc IM of epinephrine (1:1000 dilution). H1 and H2 blockers can also be given. Albuterol can be used for bronchospasm. IV epinephrine can be given for hypotension. IV steroids do nothing for the acute reaction but may decrease or prevent the late response.

Question 18

Which antihypertensive medication is relatively contraindicated in someone at risk for anaphylaxis? Why?

Answer 18

Beta-blockers are relatively contraindicated for patients with anaphylaxis because they blunt the effect of epinephrine needed to treat anaphylaxis.

Question 19

Which diseases are mediated by Type 3 immune complex hypersensitivity reactions?

Answer 19

Type 3 hypersensitivity mediated diseases include vasculitis, serum sickness, SLE, chronic autoimmune thyroiditis, pernicious anemia, and rheumatoid arthritis.

Question 20

What is the difference between the delayed Type 4 hypersensitivity reaction and the late phase of Type 1?

Answer 20

Type 4 hypersensitivity is caused by previously sensitized T-cells causing an inflammatory reaction. This is called delayed-type hypersensitivity. It is different than the late phase response in type 1 hypersensitivity which is mediated by IgE.

Question 21

What type of hypersensitivity reaction is the tuberculin test?

Answer 21

Tuberculin skin test is an example of type 3 (delayed-type) hypersensitivity.

Question 22

What is the difference between a Type 2 and a Type 5 hypersensitivity reaction?

Answer 22

Type 2 hypersensitivity (cytotoxic hypersensitivity) occurs when IgG or IgM binds to a target cell receptor and causes destruction. Type 5 hypersensitivity occurs when an autoimmune IgG reacts to and stimulates a receptor. An example, of type 5 hypersensitivity is Graves disease.

Question 23

What is the difference between acute and chronic urticaria?

Answer 23

Acute urticaria lasts <6 weeks. Chronic urticaria lasts >6 weeks.

Question 24

What causes cholinergic urticaria?

Answer 24

Cholinergic urticaria is precipitated by heat.

Question 25

What is the difference between chronic urticaria and urticarial vasculitis?

Answer 25

In urticarial vasculitis the patient has hives lasting >24 hours in a fixed location. In chronic urticaria, the hives resolve in minutes to hours and migrate to other areas.

Question 26

What is the 1st line treatment for atopic dermatitis?

Answer 26

The 1st line treatment for eczema is moisturizers.

Question 27

What do you do if you encounter an adult patient with new onset recalcitrant eczema?

Answer 27

An adult patient with new onset, recalcitrant eczema should be evaluated for cutaneous T-cell lymphoma.

Question 28

What should you do if you have a patient with a linear itchy rash below the umbilicus where the belt buckle touches the abdomen?

Answer 28

A patient who develops a rash that suggests a reaction to makeup, hair product, nickel-containing jewelry, or a belt bucket should undergo patch testing.

Question 29

What is rhinitis medicamentosa? How is it treated?

Answer 29

Rhinitis medicamentosa is a rebound congestion caused by excess use of vasoconstricting nasal drops or sprays. The treatment is discontinuation of the nasal decongestant.

Question 30

What is atrophic rhinitis? How is it treated?

Answer 30

Atrophic rhinitis is caused by atrophy of the nasal mucosa, crusting, dryness, fetor, and loss of smell. Treatment is nasal saline lavage.

Question 31

Why is it important to avoid 1st generation antihistamines in the elderly?

Answer 31

1st generation antihistamines have anticholinergic side effects which are more likely to occur in the elderly. These include blurry vision, dry mouth, and urinary retention.

Question 32

Which class of medication should be avoided for the treatment of allergic rhinitis in pregnancy?

Answer 32

Avoid decongestatnts in pregnancy as they increase the risk of congenital malformations such as gastroschisis and atresia of the small intestine.

Question 33

What is the difference between acute and chronic rhinosinusitis?

Answer 33

Acute rhinosinusitis is defined as symptoms lasting <4 weeks. Chronic rhinosinusitis is defined by symptoms lasting >4 weeks.

Question 34

When are antibiotics needed for rhinosinusitis?

Answer 34

Antibiotics should be given for rhinosinusitis only when there are severe initial symptoms including fevers, purulent nasal drainage, and facial pain OR worsening symptoms after initial improvement OR persistent symptoms with no improvement after 10 days.

Question 35

How is chronic rhinosinusitis treated?

Answer 35

Chronic rhinosinusitis is best treated with intranasal steroids and nasal saline irrigation.

Question 36

What are the two major components used to assess for asthma control?

Answer 36

The two major components to assess asthma severity are impairment (symptoms) and risk (exacerbations).

Question 37

How is uncontrolled asthma treated?

Answer 37

In uncontrolled asthma, first assess adherence to therapy. If the patient is taking the medicines correctly, then add controllers. Primary controlled therapy includes inhaled steroids alone or an ICS with a LABA.

Question 38

What are alternative agents in step up therapy for asthma?

Answer 38

Alternative agents in step up therapy for asthma include leukotriene receptor antagonists, tiotropium, theophylline, and omalizumab.

Question 39

When is drug desensitization indicated? Give two examples of when penicillin desensitization is required.

Answer 39

Drug desensitization is indicated when the patient has an IgE mediated reaction to a medicine that is the only clinically effective therapy for the condition. Two situations when PCN desensitization is needed are the pregnant patient with syphilis who has a PCN allergy and the patient with neurosyphilis with a PCN allergy.

Question 40

What is DRESS syndrome? Name a few drugs that commonly cause this reaction.

Answer 40

DRESS syndrome is is a drug rash with eosinophilia and systemic symptoms. The most common offending drugs are anticonvulsants, minocycline, and allopurinol.

Question 41

What is the difference between SJS and TEN?

Answer 41

The difference between SJS and TEN is dependent on the extent of epidermal detachment by body surface area. In SJS there is <10% involvement. In TEN there is >30% involvement.

Question 42

What are the benefits of skin testing?

Answer 42

Skin testing is quicker, more sensitive, and more cost effective than blood testing for allergies.

Question 43

When is serum antigen-specific IgE testing indicated?

Answer 43

Blood testing for allergies should be done when skin testing cannot be done such as when the patient has extensive skin disease, dermatographism, anaphylactic sensitivity to the allergen, or ongoing antihistamine use that cannot be withheld for 1-2 weeks.

Question 44

What should be done if your patient needs the influenza vaccine but gets hives with egg ingestion?

Answer 44

If the reaction to eggs was hives only, the vaccine can be given in a primary care setting. If the reaction is more severe than hives, refer the patient to an allergist for vaccine administration.

Question 45

Which vaccines are contraindicated in pregnancy? Which should be given?

Answer 45

Vaccines that are contraindicated in pregnancy include varicella, MMR, and Zostavax.

Question 46

How long should you wait to give the MMR vaccine after your patient has received a transfusion of PRBCs?

Answer 46

MMR vaccination should be delayed for 6 months after transfusion os plasma, platelets, or PRBCs.

Question 47

What physical finding is pathognomonic for urticaria pigmentosa?

Answer 47

Urticaria pigmentosa is brownish macules that form a wheal upon gentle stroking of the macule. This is called Darier sign and is pathognomonic for urticaria pigmentosa.

Question 48

Which rheumatologic disorders have a positive HLA-B27?

Answer 48

Rheumatologic disease that are associated with HLA B-27 include ankylosing spondylitis, acute anterior uveitis, reactive arthritis, psoriatic spondyloarthropathy, and juvenile rheumatoid arthritis.

Question 49

Which immune deficiency has no mature B cells? What are its symptoms?

Answer 49

Patients with X-linked agammaglobulinemia have no mature B-cells. It presents with increased susceptibility to pyogenic and encapsulated organisms. They have normal immunity to fungi, Gram-negative organisms, and viruses.

Question 50

What is the most common immunoglobulin deficiency? What are its symptoms?

Answer 50

IgA deficiency is the most common immunoglobulin deficiency. Most patients are asymptomatic. Some patients have recurrent sinopulmonary infections, recurrent giardiasis, and association with multiple autoimmune diseases, such as celiac disease and chronic autoimmune thyroiditis.

Question 51

What is Wiskott-Aldrich syndrome?

Answer 51

Wiskott-Aldrich syndrome presents with low IgM, elevated IgA, and elevated IgE. It presents with a triad of findings including eczema, immunodeficiency, and thrombocytopenia. It is X-linked.

Question 52

Know the infections associated with solid organ transplants and when each is likely to occur.

Answer 52

Infections after transplant are dependent on the length of immunosuppressant treatment. In month 1 the infections are from the donor or nosocomial infections.. In months 2-6 the infections are due to the immunosuppressant medicine and include CMV infections. After months the patient is susceptible to community-acquired infections and opportunistic infections.

Question 53

Name some factors that affect whether a patient with neutropenia develops an infection.

Answer 53

The risk for infection in neutropenia is directed related to degree and duration of neutropenia.