Chicken mim-1 protein, p33, is a heterophil chemotactic factor present in Salmonella Enteritidis immune lymphokine

Lymphokine (ILK) secreted from concanavalin A-stimulated T cells from Salmo nella Enteritidis-immune chickens is an undefined mixture of proteins that confers protection against Salmonella infectivity when administered to day- old chicks. It has previously been shown that polyclonal antibodies raised against human granulocyte colony-stimulating factor (GCSF) can neutralize t he heterophil activation that is responsible for ILK's protective effect. W estern blot analysis of ILK probed with anti-GCSF antibodies detects a prom inent protein of mass 33 kDa. We have sequenced the first 20 amino acids of this protein and found it to be identical to residues 24 to 43 of P33, a 3 26-amino acid protein of unknown function encoded by the chicken mim-1 gene . The primary structure of P33 consists of two 140-residue imperfect repeat s that are each homologous to a mammalian neutrophil chemotactic factor ter med leukocyte cell-derived chemotaxin 2 (LECT2). We have expressed mim-1 in Escherichia coli and demonstrated in vitro that recombinant P33 is chemota ctic for heterophils, the avian equivalent of mammalian neutrophils. We hav e also constructed a derivative of P33 that consists of residues 33 to 165 (P33([33-165])), the first repeat sequence of P33 that is homologous to LEC T2. P33(33-165) is chemotactic for heterophils both in vitro and in vivo, i nducing an influx of heterophils into the peritoneum in a response similar to that observed with ILK. These results suggest that P33 functions as a ch emotactic factor in chickens and that it plays an active role in ILK-mediat ed protection against Salmonella infection.