Pneumococcal cell wall phosphorylcholine elicits polyclonal antibody secretion in mice

Immunization of mice with phosphorylcholine (PC)‐bearing Staphylococcus pneumoniae Type 2, strain 36a (R36a) results in both a PC‐specific and a polyclonal increase in splenic plaque‐forming cells. The polyclonal increase was observed in all strains tested, including those bearing an X‐linked immune defect resulting in an undetectable anti‐PC immune response. The magnitude of the polyclonal response is directly related to the amount of bacterial surface PC as detected by enzyme‐linked immunosorbent assay. Congenially athymic (nude) mice mount an anti‐PC plaque‐forming cell response after R36a immunization but fail to produce a significant polyclonal response. From our results it appears that PC on the cell wall of a bacterium acts both as a polyclonal activator and a specific antigen, stimulating each by different mechanisms.