The canine lymphocyte: effect of streptolysin O on the proliferative response of canine lymphocytes.

The effects of Streptolysin O (SLO) on canine peripheral blood lymphocytes were studied using the lymphocyte blastogenesis test (LBT). Canine lymphocytes stimulated with SLO produced a response that was similar to the response obtained with the commonly used phytomitogens: phytohemagglutinin (PHA), concanavalin A (CON A) and pokeweed mitogen (PWM). When SLO was added to any of the phytomitogens and incubated with canine lymphocytes, an additive or stimulatory response was obtained. However, mixing the phytomitogens in any combination did not produce a similar additive or stimulatory response. The results were interpreted to mean that in the canine system, the binding of SLO to lymphocytes does not sterically interfere with receptors for PHA, CON A, or PWM. Additionally, SLO may stimulate a population of lymphocytes that is distinct from that stimulated by the phytomitogens. Moreover, it would appear that the phytomitogens probably stimulate the same or an overlapping population of lymphocytes. Experiments using enriched lymphoid cell populations were used to characterize the lymphocytes stimulated by phytomitogens and SLO. Lipopolysaccharides from two different bacteria were unable to cause a significant lymphoproliferative response.