Association of T cell dysfunction with the presence of IgG autoantibodies on CD4 + lymphocytes in haemophilia patients; results of a 10‐year study

HIV induces progressive dysfunction followed by numerical depletion of CD4 + lymphocytes. IgG autoantibodies and gp120‐containing immune complexes have been implicated in the pathogenesis of AIDS. We carried out a longitudinal study in 19 HIV – and 72 HIV + haemophilia patients over a 10‐year period in order to investigate a possible relationship between the occurrence of autoantibodies and CD4 + lymphocyte changes. IgM, IgG, C3d and gp120 on the surface of CD4 + lymphocytes were determined in heparinized whole blood with flow cytometry and double‐fluorescence. The in vitro response of autoantibody‐coated cells was tested in cell cultures with concanavalin A (Con A), phytohaemagglutinin (PHA), pokeweed mitogen (PWM), anti‐CD3 MoAb or pooled allogeneic stimulator cells (MLC). After a 10‐year follow up, 12 of 71 HIV + and 16 of 19 HIV – haemophilia patients showed no evidence of immunoglobulins on circulating CD4 + lymphocytes. HIV – haemophilia patients without autoantibodies had CD4 + and CD8 + cell counts in the normal range (957 ± 642/μl and 636 ± 405/μl) and normal T cell responses in vitro (mean relative response (RR) ≥ 0.7). In contrast, HIV + haemophilia patients showed immunological abnormalities which were associated with the autoantibody and immune complex load of CD4 + blood lymphocytes. HIV + patients without autoantibodies had a mean CD4 + lymphocyte count of 372 ± 274/μl, a mean CD8 + lymphocyte count of 737 ± 435/μl, and normal T lymphocyte stimulation in vitro (mean RR ≥ 0.7). HIV + patients with complement‐fixing IgM on CD4 + lymphocytes had somewhat lower CD4 +  (255 ± 246/μl, P  = NS) and CD8 + (706 ± 468/μl, P  = NS) lymphocyte numbers, and also normal T lymphocyte stimulation (mean RR ≥ 0.7) in vitro . However, patients with complement‐fixing IgG autoantibodies showed a strong decrease of CD4 +  (150 ± 146/μl, P  < 0.02) and CD8 +  (360 ± 300/μl, P  < 0.02) lymphocytes and impaired CD4 + lymphocyte stimulation in vitro with a mean RR of 0.5 ± 0.5 for Con A ( P  = NS), 0.7 ± 0.8 for PHA ( P  < 0.03), 0.4 ± 0.4 for PWM ( P  = NS), 0.8 ± 1.2 for anti‐CD3 MoAb ( P  < 0.04) and 0.7 ± 1.0 for pooled allogeneic stimulator cells ( P  = 0.05). Patients with gp120‐containing immune complexes on CD4 + blood lymphocytes demonstrated strongly decreased CD4 + (25 ± 35/μl, P  < 0.0001) and CD8 + (213 ± 212/μl, P  < 0.006) lymphocyte counts as well as strongly impaired T lymphocyte responses in vitro upon stimulation with PHA (RR 0.2 ± 0.1, P  < 0.02), PWM (RR 0.2 ± 0.2, P  = 0.05), anti‐CD3 MoAb (RR 0.1 ± 0.1, P  < 0.04), and allogeneic stimulator cells (RR 0.2 ± 0.1, P  < 0.02). These data led us to speculate that autoantibody formation against CD4 + lymphocytes is an important mechanism in the pathogenesis of AIDS. We hypothesize that autoantibodies against circulating CD4 + lymphocytes inhibit CD4 + cell function, especially the release of cytokines, and induce CD4 + cell depletion. The reduction and dysfunction of CD4 + lymphocytes may be responsible for the CD8 + cell depletion observed in HIV + patients.