CD38- B cells in the mouse Peyer's patch and in immunized mouse spleen

The relationship between CD38 expression on activated germinal center (GC) cells and mature differentiated B cells was studied in the mouse. CD38 is expressed on follicular cells in the Peyer's patch but is lost as B cells differentiate in Peyer's patch germinal centers giving rise to a population of B220 CD38" B cells. These cells are larger than B220 CD38 follicular B cells and have lower surface expression of CD2I, CD23, CD62L, IgD, and IgM with increased CD95 expression. This unique population is also found in the spleens of immunized but not control mice suggesting that antigen stimulated GC formation is involved in production of B220 CD38" B cells. In sections from Peyer's patch and spleens of immunized mice the GC are predominately CD38" but some CD38 cells exist and these cells most likely represent an early stage in germinal center B cell development. CD38 remains high on isotype switched cells that still express IgM but is downregulated on cells that have completed the isotype switch to IgA in the Peyer's patch and no longer co-express IgM. These results are in contrast to studies of human CD38 where high expression of CD38 is a marker for GC B cells. In mice, CD38 expression is related to B cell differentiation and in particular the formation of mature isotvoe switched B cells, however it is not, as in humans, expressed on the majority of GC B cells.