Characterization of the NF-κB/Rel protein heterodimers present in nonnuclear fractions of resting human neutrophils. Following NP40 lysis of neutrophils, nonnuclear fractions were immunoprecipitated using antisera to individual NF-κB/Rel proteins, and immunoprecipitates (2.5 × 10⁶ cell-equivalents) were analyzed by immunoblot using an antiserum to the N-terminal region of p65/RelA (no. 1207, left panel), or an antiserum to c-Rel (no. 265, right panel). This experiment is representative of at least three. MW, molecular weight markers (in kD); ipp, antiserum used for immunoprecipitation.