Surface immunoglobulin phenotype of complement receptor-positive and complement receptor-negative B cells of normal andxid immunodeficient mice

Abstract

Single‐ and dual‐parameter fluorescence‐activated cell sorter analyses of complement receptor‐positive and ‐negative (CR⁺ and CR⁻) splenic B cells of normal and xid immunodeficient mice were performed to determine the frequencies of surface (s) IgM⁺ and sIgD⁺ cells, as well as the quantities of sIgM and sIgD on these cells. Single parameter analysis revealed identical frequencies of sIgM⁺ and sIgD⁺ cells in the CR⁺ B cell population of normal mice. In contrast, the percentage of sIgM⁺ cells exceeded that of sIgD⁺ cells in the CR⁻ normal and CR⁺xid B cell population to a similar extent. CR⁻xid B cells showed an even greater discrepancy between sIgM⁺ and sIgD⁺ cells. Dual‐parameter analysis of CR⁺ normal B cells showed the typical sIg phenotype of mature B cells, i.e. an intermediate density of sIgM and a high density of sIgD. The CR⁺xid B cell population displayed an increase in cells with high sIgM and no‐to‐low sIgD and a decrease in cells with intermediate sIgM and high sIgD when compared to CR⁺ normal cells. CR⁻ B cells from normal and xid immunodeficient mice were similar in that both consisted largely of a cell population with low sIgM and no‐to‐low sIgD. However, the CR⁻ normal B cell population also contained cells with intermediate sIgM and high sIgD, which were lacking in the CR⁻xid cell population. Similar results were obtained when CR⁺ and CR⁻ B cells from normal and xid mice were purified from a small resting B cell population, isolated by elutriation. This indicates that the sIg phenotype of CR⁻ cells is not due to the presence of large cells which have lost sIgD during activation.