Rat MHC class I Abs bind to the rat PMNs. Rat PMNs were isolated, incubated with PE-labeled isotype, OX18, or OX27, and fixed in paraformaldehyde. PMNs incubated with the OX18 and OX27 antibodies bound to the PMNs, as demonstrated by the fluorescent shift compared with the labeled isotype controls via flow cytometry (n = 3).