Expression patterns of six Kunitz/BPTI genes in Ixodes scapularis identified in our study. The number of ESTs for each gene is plotted against different stages of tick blood feeding (ISUF, IS6-12, S18-24 and ISA72). The details of the four stages are described in the Methods. Different genes are indicated by different colored makers. Expression of genes (Isc.190, Isc.255, Isc.196, Isc.180 and Isc.179) arises at 72 hours post host attachment (Expression pattern 1). However, expression of gene Isc.218 begins at 6-12 hours (17 ESTs), elevates strikingly at 18-24 hours (259 ESTs) and decreases rapidly at 72 hours (2 ESTs) post host attachment (Expression pattern 2).