MURINE COMPLEMENT RECEPTOR GENE-EXPRESSION - CR-2 GENE TRANSCRIPTS ARE DEPRESSED DURING A HIGH-DOSE MICROBIAL CHALLENGE

The murine Cr2 gene encodes mRNA that produce two protein products pre dicted to be approximately 145,000 M(r) (Cr2-145) and 190,000 M(r) (Cr 2-190). All cells examined which express the Cr2 gene produce transcri pts encoding both the Cr2-145 and Cr2-190 proteins: both transcripts a re constitutively expressed by mature B cells. To determine if Cr2 exp ression could be altered by activating splenic B cells, splenic cultur es were incubated with lipopolysaccharide (LPS) and cell surface Ig ch ains were cross-linked with anti-mu. In the presence of LPS and anti-m u both Cr2 and Oct-2 transcripts were diminished while the control bet a-actin transcript levels remained unchanged. However, when LPS alone was added, only the Cr2 transcript levels were diminished. To test if these findings could be reproduced in vivo, animals were provided with a peritoneal injection of either Escherichia coli or Listeria monocyt ogenes and transcript levels analysed. The quantities of both Cr2 tran scripts, as well as those encoding Oct-2, were substantially reduced i n splenocytes and peripheral lymphatic tissues obtained from these inf ected mice while those encoding the mouse Crry protein, the B-cell mar ker CD19 and beta-actin remained unchanged. These data suggest that wh en confronted with a major bacterial infection, murine B cells respond by shutting down synthesis of transcripts encoding the Cr2 and Oct-2 gene products.