In vitro stimulation of human peripheral blood lymphocytes by Neisseria meningitidis

Abstract Heat-killed Neisseria meningitidis was found to be mitogenic for human peripheral blood lymphocytes (PBL). Separation of lymphocytes by rosetting with sheep erythrocytes indicated that both rosette-forming cells (E⁺, T-enriched) and nonrosetting cells (E⁻, B-enriched) were induced to proliferate by the bacteria. Following meningococcal stimulation, E⁻ cells and PBL displayed proliferative responses of similar magnitude and followed essentially the same kinetics with peak responses occurring after 3–4 days of culture. By comparison, E⁺ lymphocytes gave significantly higher responses and required a longer incubation period (5–7 days) to reach maximum levels of proliferative activity.