Glossary of HD - SGPSS 5 (B-Cell Deficiency)

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What is X-Linked Agammaglobulinemia (XLA)?
An X-linked defect in B-Cell development which prevents differentiation and proliferation of B-Cells, absence of plasma cells, absence of germinal centers, and very low levels of circulating immunoglobulins.
Why would a patient with XLA present with persistent infection?
Lack of Ab's lead to an inability to opsonize capsular antigens and suboptimal binding to C3b and Fc-gamma receptors on neutrophils resulting in ineffective phagocytosis.
What kind of therapy is appropriate for XLA?
IgG replacement therapy (passive immunity).
What is Severe Combined ImmunoDeficiency (SCID)?
Insufficient lymphocytes resulting in a broad inability to respond to infection early after birth.
What cells will be markedly reduced in SCID?
Neutrophils, platelets, lymphocytes due to an early lineage defect in hemopoietic stem cells in the bone marrow.
RBC's are not affected due to an early break in lineage.
What would an electrophoresis of a patient with SCID look like?
Reduced globulins.
What would a FACS analysis (separate and measure different cell types) of SCID look like?
Absence of all lymphocytes.
What is Mixed Lymphocyte Testing and why is it useful?
Test to find the best donor-recipient match. Mix each blood and find the least amount of proliferation (with one side radioactively suppressed).
What is MHC Typing and what is it useful for?
One parent gives a set of MHC's to the child, and it helps to determine positive matches for organ transplant. What else??
What are the symptoms of a Plasma cell defect?
High number of circulating lymphocytes, but low serum levels of IgG.
What prevents B-Cell maturation in patients with a Plasma cell defect?
No germinal centers for isotype switching and terminal differentiation.
What is the difference between XLA and plasma cell defects?
XLA would have no Ab's at all.
Where might the possible defects be in the plasma cell defect?
Defective B-cell differentiation, defective germinal centers, defective cytokines, defective B-cell to Th2 cell cross-talk.
What are patients with plasma cell defects more susceptible to?

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