Activation of human lymphocyte subpopulations by Mycoplasma pneumoniae

B- and T-cell-enriched preparations of lymphocytes from human blood (5 cases), adenoids (10 cases), and tonsils (4 cases) were examined for the in vitro stimulation response to Mycoplasma pneumoniae (MP). B lymphocytes did not respond to MP by DNA synthesis except for the B cells from one adenoid. T lymphocytes and nonfractionated lymphocytes from blood, from three of the adenoids and two of the tonsils showed a stimulation response to MP. Nonfractionated adenoid lymphocytes from altogether 22 children were examined, and a stimulation response to MP was demonstrated in 8 cases. Lymphocyte cultures from 11 adenoids and 2 tonsils were examined for MP-induced non-antigen-specific antibody production by a hemolytic plaque assay. In all these cultures MP activated production of antibody-secreting cells to sheep erythrocytes. It is concluded that MP can induce non-antigen-specific angibody production in human B lymphocytes without stimulating DNA synthesis in these cells. The proliferative response of adenoid, tonsil, and blood lymphocytes to MP is interpreted as an antigen-specific T-cell response.