A kinetic analysis of the expression of mast cell protease mRNA in the intestines of Nippostrongylus brasiliensis-infected rats.

To study the kinetics and the phenotype of the mast cells (MC) arising during infection with the nematode Nippostrongylus brasiliensis, monospecific cDNA probes for nine different MC proteases were used in a Northern blot analysis of RNA from the small intestine of infected rats. The expression was analyzed at four individual time points during infection, day 0 (before infection), and days 7, 12 and 16 post infection. A dramatic increase in mRNA for rat mast cell protease (RMCP)-2, the major mucosal MC protease in the rat, was observed, beginning around day 7 after infection and peaking around day 12. At day 16 the expression was already beginning to decline. An almost identical pattern of mRNA expression was detected for the RMCP-8 subfamily of rat MC proteases (RMCP-8, -9 and -10) and for two additional rat serine proteases, the chymases RMCP-3 and -4. No simultaneous increase in the proteases known to be expressed preferentially by mature connective tissue MC (RMCP-1, -6 and -7) was observed. This is consistent with our finding that the expansion of MC in the intestines of parasite-infected animals was limited, almost exclusively, to the mucosal MC population. However, a minor increase in RMCP-5 and MC carboxypeptidase A (CPA) mRNA was detected at day 12 after infection, suggesting a derivation of mucosal MC from an expanding RMCP-5- and CPA-positive population of MC precursors.