Mutation Analysis in X-linked Recessive Congenital Immunodeficiency Syndromes

Baek, Hee Jo; Choi, Seung Hee; Sohn, Kyoung Ran; Kook, Hoon; Kim, Seok Ju; Song, Eun Song; Han, Dong Kyun; Hwang, Tai Ju

Abstract

In patients and their families who had relevant clinical findings and compatible immunologic data suggestive of X-linked congenital immunodeficiency syndromes, the authors tried to identify the genetic abnormalities employing the flow cytometric analysis of the gene products using appropriate monoclonal antibodies (MoAb). Polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) and direct sequencing of gene mutation were also applied. In a family with a X-linked agammaglobulinemia (XLA), 3 patients and 4 obligate carriers were identified. Flow cytometric analysis of Btk protein in mononuclear cells was not detected in the patients, while significantly reduced in the carriers. A single base pair mutation (T-->C) in Btk exon 3, which encodes the PH domain, was demonstrated in 3 XLA patients. The patient with X-severe combined immunodeficiency (X-SCID) revealed negligible expression of common gamma chain (gammac) using anti-CD132 MoAb. He had a C-->T point mutation at nucleotide position 690 of exon 5, as determined by direct sequencing and PCR-RFLP. The patient's mother was a heterozygous carrier. In a patient with hyper IgM syndrome, activated lymphocytes failed to express CD40L on their surface, and a T-->C missense mutation was found at exon 5. His mother and sister were found to be carriers. The patient with Wiskott-Aldrich syndrome had a C-->T point mutation in exon 7 that resulted in an amino acid change in codon 211. The present study identified gene mutations responsible for 4 different X-linked congenital immunodeficiency syndromes. By applying those techniques an accurate diagnosis of the genetic abnormalities along with identification of carriers is feasible, providing the possibility of therapeutic intervention as well as the clues for genetic counseling.