Fig. 3. Schematic model of LRIM1 and CTL (CTL4 and CTLMA2) protein action during Plasmodium development in the mosquito midgut. During or soon after invasion of the midgut epithelium (four downward-oriented arrows), three out of four invading ookinetes are eliminated, partly through the antagonistic action of LRIM1 (upward-oriented arrows). However, CTL4 and, to a lesser extent, CTLMA2 protect the remaining ookinetes from the melanization response (slanted black bars); melanization also requires LRIM1 activity (horizontal arrow).