Defective integration of activating signals derived from the T cell receptor (TCR) and costimulatory molecules in both CD4+ and CD8+ T lymphocytes of common variable immunodeficiency (CVID) patients.

CVID is characterized by hypogammaglobulinaemia and impaired antibody production. Previous studies demonstrated defects at the T cell level. In the present study the response of purified CD4+ and CD8+ T lymphocytes to stimulation with anti-TCR monoclonal antibody (the first signal) in combination with anti-CD4 or anti-CD8, anti-CD2 and anti-CD28 MoAbs (the costimulatory signals) was investigated. Both CD4+ and CD8+ T cells from the patients showed significantly reduced IL-2 release following stimulation via TCR and costimulation via CD4 or CD8 and CD2, respectively. However, normal IL-2 production following TCR plus phorbol myristate acetate (PMA) costimulation and normal expression of an early activation marker, CD69, after TCR+CD28 stimulation indicated that TCR was able to transduce a signal. Furthermore, both IL-2 and IL-4 release were impaired in CD4+ lymphocytes following TCR+CD28 stimulation. In addition, stimulation via TCR+CD28 resulted in significantly decreased expression of CD40 ligand in the patients. These results suggest that the integration of activating signals derived from the TCR and costimulatory molecules is defective in CVID patients; the defect is not confined to costimulation via a single molecule, or restricted to cells producing Th1-type cytokines such as IL-2, and is expressed in both CD4+ and CD8+ T cell subsets.