Human polymorphonuclear neutrophils express a B7-1-like molecule

Polymorphonuclear neutrophils (PMN) are part of the innate immune system an d are first-hue effector cells in acute inflammatory responses. On activati on PMNs secrete cytokines and oxygen metabolites that might be involved in the regulation of the acquired immune response. We show here that periphera l blood PMNs constitutively express a B7-1-like molecule as detected by imm unostaining with several B7-1 antibodies. Reverse transcriptase-polymerase chain reaction using three sets of printers spanning different regions of B 7-1 indicate dissimilarities at the mRNA level. B7-1 mRNA is expressed in b one marrow cells and Lipopolysaccharide (LPS)-stimulated but not in unstimu lated PMNs. The B7-1-like molecule is localized to the cytoplasmic granules and translocated to the cell surface after stimulation with LPS or interle ukin-12 in some donors. Binding of CTLA4-Ig suggests that the B7-1-like mol ecule can interact with functional B7 ligand and mig ht be important in the immunobiology of PMNs.