Human polymorphonuclear neutrophils express a B7-1-like molecule.

Polymorphonuclear neutrophils (PMN) are part of the innate immune system and are first-line effector cells in acute inflammatory re- sponses. On activation PMNs secrete cytokines and oxygen metabolites that might be involved in the regulation of the acquired immune response. We show here that peripheral blood PMNs constitu- tively express a B7-1-like molecule as detected by immunostaining with several B7-1 antibodies. Re- verse transcriptase-polymerase chain reaction us- ing three sets of primers spanning different regions of B7-1 indicate dissimilarities at the mRNA level. B7-1 mRNA is expressed in bone marrow cells and lipopolysaccharide (LPS)-stimulated but not in un- stimulated PMNs. The B7-1-like molecule is local- ized to the cytoplasmic granules and translocated to the cell surface after stimulation with LPS or interleukin-12 in some donors. Binding of CTLA4-Ig suggests that the B7-1-like molecule can interact with functional B7 ligand and might be important in the immunobiology of PMNs. J. Leukoc. Biol. 66: 945-952; 1999.