condition resulting from a genetic or developmental defect in the immune system
is called a primary immunodeficiency. In such a condition, the defect is
present at birth, although it may not manifest itself until later in life. Most
of the primary immu-nodeficiencies are inherited from parents to offsprings.
Primary immunodeficiency may affect either adaptive or innate immune functions.
Most defects that lead to immunodeficiencies affect either myeloid or lymphoid
cell lineages. The lymphoid cell disorders may affect T cells, B cells, or both
B and T cells, whereas the myeloid cell disorders may affect phagocytic
Primary immunodeficiency diseases can be classified as:
(a) B-cell immunodeficiencies,
(b) T-cell immunodeficiencies,
(c) combined B-cell and T-cell deficiencies,
(d) complement immunodeficiencies, and