Immunodeficiencies of the Adaptive Immune System

Question 1

Discuss X-linked Agammaglobulinemia

Answer 1

Failure of B-cell precursors to develop into mature B cells.

Question 2

Describe clinical presentation of X-linked agammaglobulinemia.

Answer 2

All Ig isotypes are decreased; Mature B lymphocytes and plasma cells are absent. Normal T cell function

Question 3

Discuss Selective IgA deficiency

Answer 3

Inability to make IgA; Normal levels of other Igs. Frequent respiratory and GI tract infections.

Question 4

Discuss Common Variable Immunodeficiency (CVID)

Answer 4

Reductions in IgG and IgA; Defects in Ig alpha chains or B cell differentiation. Antibody production is impaired and plasma cells are absent.

Question 5

Discuss Hyper IgM syndrome

Answer 5

Defective isotype switching in B cells resulting in high IgM levels with little to no IgG, IgA or IgE.

Question 6

Describe Hyper IgM syndrome in clinical presentation.

Answer 6

No memory B cells, No germinal center; Myelocyte/Promyelocyte differentiation block

Question 7

Discuss Bare Lymphocyte Syndrome (MHC2 deficiency)

Answer 7

Absence of MHC2 expressoion; No humoral or cell mediated immune response. T and B cell numbers are normal

Question 8

Discuss Wiskott-Aldrich syndrome

Answer 8

Defective gene for WAS protein which functions in the immune synapse formation between T cells and APCs

Question 9

How does Wiskott-Aldrich present clinically?

Answer 9

Lymphopenia, Eczema and thrombocytopenia; IgM levels are low, IgE and IgA are high

Question 10

Discuss X-linked SCID

Answer 10

Marked by presence of small thymus which has no Hassall’s corpuscles and is devoid of lymphocytes; No tonsils are present

Question 11

Discuss Adenosine deaminase deficiency

Answer 11

An enzye thats involved in purine metabolism and adenosine homeostasis. Catalyzes the deamination of adenosine and 2-deoxyadenosine; Two toxic metabolites. Impacts developing T cells. Lymphopenia

Question 12

Discuss DiGeorge Syndrome.

Answer 12

Abnormal neural crest cell migratioin. Thymic aplasia, no T cells in lymph nodes, spleen or peripheral blood

Question 13

How does DiGeorge Syndrome present?

Answer 13

Congenital cardiac defects, thymic aplasia, hypocalcemia due to absence of parathryoid glands. Downward slanting eye, low set ears

Question 14

Describe the acute phase of AIDS

Answer 14

Initial response to HIV infection in immunocompetent patient.

Question 15

Describe the chronic phase of AIDS

Answer 15

CD4 cell loss increases in magnitude; AIDS diagnosed when CD4 count is below 200 cells per microliter