Upon entering the mammalian bloodstream, L. major meets the focal point of infection, the macrophage. As a result of two surface molecules, the protease gp63 and a lipophosphoglycan, promastigotes are able to bind to several macrophage receptors. Promastigote attachment to macrophages is facilitated by a number of receptors, including complement receptors CR1 and CR3, and the receptor for advanced glycosylation end products. Activation of complements occurs far from the cell membrane, and insertion of the membrane attack complex does not occur. This action is what allows the parasite to avoid being lysed, and to persist within the host's macrophages. In cattle Th1 and Th2 cells are an important part of the response. Neither cell type expresses exclusively IFNγ or IL-4 for L. major – Brown et al. 1998 find they express both in cattle. The bovine myeloid antimicrobial peptide has leishmanicidal activity and may be usable in vivo in cattle infection. Lynn et al., 2011 obtain good results against two strains of the parasite, using two isoforms of BMAP-28, the retro-inverso and the D-amino acid.
