A case of selective immunoglobulin G deficiency: Analysis of coculture with normal lymphocytes in vitro

A 3.3-year-old boy with intractable infection and selective immunoglobulin G (IgG) deficiency had a normal percentage of T cells (61%) and surface IgG-bearing cells (4.4%). The serum contained an increased amount of immunoglobulin A (IgA) (488 mg/dl), immunoglobulin M (IgM) (420 mg/dl), and a trace amount of IgG (40 mg/dl). Coculture studies showed that the patient's T cells suppressed the generation of cytoplasmic-IgG-positive cells from a mixture of normal T and B cells after stimulation with pokeweed mitogen, whereas the generation of cytoplasmic-IgA-and cytoplasmic-IgM-positive cells was within normal range. Furthermore, the patient's T cells did not cooperate with normal B cells and his B cells did not differentiate into cytoplasmic-immunoglobulin-positive cells, despite the presence of normal T cells.