Functional differences associated with quantitative distribution of membrane immunoglobulin, Fc receptors and Ia on mouse B cells.

Murine splenic B cells were stained with antibodies against mIg, Ia or FcR and then separated on the fluorescence-activated cell sorter on the basis of quantitative differences in marker expression; that is, they were fractionated into subpopulations bearing high or low densities of the marker. The separated cells were then tested for their relative capacities for T-dependent primary and secondary antibody responses, and for lipopolysaccharide responsiveness. There was no association between the surface density of any of these markers and the ability of the cells to proliferate in response to lipopolysaccharide. However, a high level of surface Ia was associated with good primary and secondary T-dependent responses. The density of mIg or of FcR showed no association with the capacity for primary responses, but a low density of these two markers, especially FcR, was correlated with good secondary responsiveness. Thus, subpopulations of B cells selected on the basis of quantitative levels of membrane markers can also be distinguished by their functional properties.