B lymphocyte activation by insoluble anti-mu antibodies in patients with systemic lupus erythematosus.

In order to study the capacity of anti-immunoglobulin (Ig) antibodies to induce proliferative responses in peripheral blood mononuclear cells (PBC) from patients with systemic lupus erythematosus (SLE), anti-mu coupled to Sepharose beads (anti-mu) was used as a polyclonal activator. In 18 patients, a strong proliferative response was associated with inactive disease, and the response was lower in clinical active disease (P less than 0.02). An inverse correlation could also be observed in six patients who were studied longitudinally (P less than 0.01). These results indicate that anti-mu responsiveness is closely related to disease activity in SLE. In addition, sequential data obtained from two patients during an early stage of clinical deterioration suggest that a low anti-mu response might be an early indicator of a clinical relapse. In the patients investigated, the anti-mu response was not correlated with the response to pokeweed mitogen (PWM), or with the quantity of B cells. When T cell depleted cell fractions were studied, marked increases in the proliferative responses to anti-mu were observed in some patients. These studies suggest that the response to anti-mu might be modified by T cells to a variable extent in patients with SLE.