Major histocompatibility complex class III genes and susceptibility to immunoglobulin A deficiency and common variable immunodeficiency.

TLDR

We propose that IgA deficiency and common variable immunodeficiency may represent polar ends of a single genetic spectrum. We analyzed MHC haplotypes in 12 IgA‑D and 19 CVID patients and 79 relatives from 21 families. Haplotypes were defined by polymorphic markers for 11 genes between HLA‑DQB1 and HLA‑A, with families containing multiple immunodeficient members. A small set of class III haplotypes, present in 77 % of affected individuals and shared by both IgA‑D and CVID, co‑occur with frequent C4A deletions and C2 rare alleles, pointing to a susceptibility locus between C4B and C2.

Abstract

We have proposed that significant subsets of individuals with IgA deficiency (IgA-D) and common variable immunodeficiency (CVID) may represent polar ends of a clinical spectrum reflecting a single underlying genetic defect. This proposal was supported by our finding that individuals with these immunodeficiencies have in common a high incidence of C4A gene deletions and C2 rare gene alleles. Here we present our analysis of the MHC haplotypes of 12 IgA-D and 19 CVID individuals from 21 families and of 79 of their immediate relatives. MHC haplotypes were defined by analyzing polymorphic markers for 11 genes or their products between the HLA-DQB1 and the HLA-A genes. Five of the families investigated contained more than one immunodeficient individual and all of these included both IgA-D and CVID members. Analysis of the data indicated that a small number of MHC haplotypes were shared by the majority of immunodeficient individuals. At least one of two of these haplotypes was present in 24 of the 31 (77%) immunodeficient individuals. No differences in the distribution of these haplotypes were observed between IgA-D and CVID individuals. Detailed analysis of these haplotypes suggests that a susceptibility gene or genes for both immunodeficiencies are located within the class III region of the MHC, possibly between the C4B and C2 genes.