Defect of T helper lymphocytes, as identified by the 5/9 monoclonal antibody, in patients with common variable hypogammaglobulinaemia.

Peripheral blood lymphocytes from 17 patients with common variable hypogammaglobulinaemia (CVH) were tested for reactivity with the 5/9 monoclonal antibody which reacts with about 15% of normal T-PBL in which all helper activity is found. In PBL from CVH patients, the proportions of OKT4 and OKT8 positive cells were also determined. Five patients had normal percentages of 5/9 cells and a normal OKT4/OKT8 ratio. Twelve patients had significantly decreased (or absent) 5/9 lymphocytes. Among these, five had decreased 5/9 cells and a normal OKT4/OKT8 ratio and seven had decreased 5/9 cells and an inversion of the OKT4/OKT8 ratio. The deficiency of the helper phenotype T cell subpopulation identified by the 5/9 monoclonal antibody in many patients with CVH may be relevant in the pathogenesis of this disease.