Modulation of human B cell responses by a monoclonal antibody to an activation antigen 4F2.

Antigen specific human antibody responses can be modulated in vitro by the addition of 4F2 antibody, a monoclonal antibody (MoAb) which recognizes an antigen on activated T cells and B cells. Specific antibody responses induced with the antigen are suppressed by the addition of 4F2. However, specific antibody responses induced with the polyclonal activator, pokeweed mitogen (PWM), are significantly enhanced by the addition of 4F2. Proliferative responses to both antigen and PWM are suppressed by the addition of 4F2. The enhancement of PWM stimulated responses by 4F2 is mediated by T cells. However, in the absence of T cells, 4F2 can directly inhibit antigen specific B cells. Polyclonal Ig production stimulated by PWM was also enhanced by 4F2. Thus, the immunomodulating effects of the 4F2 MoAb are the result of a balance of enhancement and suppression mediated at the T cell and the B cell level, respectively.