Modulation of T and B cell proliferative responses by factors present in rat salivary glands

Rat salivary gland culture supernatants (SGSN) were shown to inhibit the proliferation of rat spleen cells induced by the mitogens concanavalin A (ConA), phytohaemagglutinin (PHA), pokeweed mitogen (PWM), lipopolysaccharide (LPS) and S. typhimurium mitogen (STM). The responses of B cells were more markedly inhibited than the responses of T cells. Factors contained in SGSN which had a molecular weight smaller than 3500 inhibited all responses, whereas factors greater than 3500 only inhibited responses induced by PWM, LPS or STM. Factors present in SGSN also inhibited the proliferation of two B cell hybridoma cell lines, as well as the IL-2-responsive cell line CTLL-2 and the IL-4-responsive cell line CT.4S. However, SGSN factors having a molecular weight greater than 3500 did not inhibit CTLL-2 proliferation. These data indicate that rat salivary glands contain factors which differentially regulate T and B cell proliferative responses in vitro and which may modulate localized immune responses in the salivary gland in vivo.