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Ligation of CD45 on B cells can facilitate production of secondary Ig isotypes
1Department of Biology, University of Pennsylvania, Philadelphia 19104.
The possibility that isotype switching in B cells may be affected by engagement of the CD45 molecule on B cells has been investigated in microcultures containing limiting numbers of B cells and nonlimiting numbers of both alloreactive Th cells and purified dendritic cells (DC). Addition of Abs to the B cell-specific isoform, B220, to the microcultures leads to an increase in the proportion of B cell clones that secrete secondary Ig isotypes. In the presence of anti-CD45 Ab, microculture wells show a 39% frequency of secondary isotypes (560/1440) compared with a 11% frequency in control microcultures (89/780). Cross-linking appears to enhance this effect. Even in cultures of B cells and DC without T cells, addition of anti-B220 induces isotype switching in a significant number of microwells. Cross-linking and capping B220 molecules results in co-capping of surface Ig and MHC class II molecules. The results suggest that signal transduction through the CD45 molecule may affect pathways involved in isotype switching.
The possibility that isotype switching in B cells may be affected by engagement of the CD45 molecule on B cells has been investigated in microcultures containing limiting numbers of B cells and nonlimiting numbers of both alloreactive Th cells and purified dendritic cells (DC). Addition of Abs to the B cell-specific isoform, B220, to the microcultures leads to an increase in the proportion of B cell clones that secrete secondary Ig isotypes. In the presence of anti-CD45 Ab, microculture wells show a 39% frequency of secondary isotypes (560/1440) compared with a 11% frequency in control microcultures (89/780). Cross-linking appears to enhance this effect. Even in cultures of B cells and DC without T cells, addition of anti-B220 induces isotype switching in a significant number of microwells. Cross-linking and capping B220 molecules results in co-capping of surface Ig and MHC class II molecules. The results suggest that signal transduction through the CD45 molecule may affect pathways involved in isotype switching.