Molecular cloning of a murine fibronectin receptor and its expression during inflammation. Expression of VLA-5 is increased in activated peritoneal macrophages in a manner discordant from major histocompatibility complex class II

Human fibronectin receptor (VLA-5) α and β chain probes were used to identify their mouse homologues in a thioglycollate-elicited peritoneal exudate cell cDNA library. Sequence analysis of both α and β chain-related murine clones revealed ~90% homology to their human counterparts by both nucleotide and derived amino acid sequence comparisons. Detectable α chain transcripts were seen predominantly in total RNA of peritoneal macrophages. β chain expression, however, was detected at higher levels in lung, heart, brain, and kidney, suggesting the presence of a large murine VLA family similar to the human family. Analysis of levels of expression comparing resting peritoneal macrophages with macrophages elicited using inflammatory stimuli indicated that α chain message and surface VLA-5 expression were significantly increased using thioglycollate or Listeria monocytogenes as stimuli to elecit cells. Interestingly, β chain message was unaffected by these inflammatory stimuli, suggesting that VLA-5 expression is regulated by VLA-5 α chain message levels. These results indicate that macrophage VLA-5 expression can be modulated in vivo and may provide an important mechanism by which macrophages are recruited to or adhere to fibronectin in inflammatory foci.