Polyclonal activation of human peripheral blood B lymphocytes: III. Cellular interaction and immunoregulation of immunoglobulin-secreting cells induced by formaldehyde-fixed Salmonella paratyphi B

Abstract

We studied the interactions between regulatory cells and B cells in cultures of peripheral blood leukocytes (PBL) stimulated with various polyclonal B-cell activators, i.e., pokeweed mitogen (PWM), Staphylococuss aureus Cowan I (SAC), and Salmonella paratyphi B (SPB). Polyclonal B-cell activation in cultures was evaluated by enumeration of cells secreting immunoglobulin (Ig) and/or by quantitation of Ig released into culture supernates. Cord blood T cells and PBL after activation with concanavalin A or by prolonged incubation were used as sources of suppressor T cells. In coculture experiments, SPB-induced generation of Ig-secreting cells (ISC) was not affected, whereas PWM-induced generation of ISC was inhibited by suppressor T cells. The effects of suppressor T cells on SAC-induced generation of ISC was variable. Monocytes were required for PWM-induced generation of ISC; in contrast, SPB- and SAC-induced B-cell activation were not dependent on monocytes. Moreover, SPB-induced B-cell activation appeared to be susceptible to monocyte-mediated suppression. These results indicate that monocyte-mediated suppression is exerted directly on B cells rather than indirectly via suppressor T cells.