The HLA System

Deficiencies of HLA MoleculesA clinician's attention is normally drawn to a system only when it malfunctions. The HLA system is no exception in this regard, but in contrast to other systems, it also arouses interest when it functions well — too well, in fact. The most dramatic malfunction of the HLA system occurs when its genes falter in their expression, resulting in HLA class I or class II deficiencies (the bare lymphocyte syndrome, in which “bare” refers to the low level of HLA molecules on the cell surface). Severe cases of HLA deficiencies are, in fact, not caused by . . .