A functional defect in the early phase of the immune response observed in patients with hemophilia A

In search of a functional immunological defect in patients with hemophilia A, we investigated the early phase of the immune response and found a deficiency in the monocyte-T cell interaction after in vitro exposure to a bacterial antigen. T-cell proliferation in response to Escherichia coli-pulsed autologous monocytes was significantly (P less than 0.025) reduced in hemophiliacs [mean dpm +/- SEM (n = 25): 9036 +/- 2600] as compared to healthy controls [mean dpm +/- SEM (n = 24): 17,812 +/- 2985]. This functional defect was expressed in a severe form (antigen-induced monocyte-T cell interaction less than or equal to 2000 dpm) in both HTLV III antibody-positive and -negative patient populations. Significantly decreased T-helper/T-suppressor-cell ratios (mean dpm +/- SEM: patients 1.47 +/- 0.13; controls 2.04 +/- 0.11; P less than 0.001)--but without a concomitant reduction in the absolute number of T-helper cells--could also be observed.