Polymorphism of class A scavenger receptors in C57BL/6 mice

Scavenger receptors class A (SR-A) have been hypothesized to regulate the d evelopment of atherosclerotic lesions through recognition of modified low d ensity lipoprotein (LDL) and macrophage adhesion to substrata, Supporting d ata have been collected from studies using the monoclonal antibody 2F8, an antibody developed from the BALB/c strain-derived macrophage cell line, RAW .264. Although 2F8 immunostained both cultured peritoneal macrophages (MPM) and thymic macrophages from Swiss, BALB/c, and DBA/2 mice, no immunostaini ng was detected in cells and tissues from C57BL/6 mice, one of the most com monly used atherosclerosis-susceptible mouse strains. Similarly, 2F8 detect ed SR-A protein in MPM by Western blotting in all strains except C57BL/6, H owever, a guinea pig antiserum developed to a fusion protein of the extrace llular SR-A domain detected appropriately sized bands in all strains. Incub ation with 2F8 antagonized acetylated low-density lipoprotein (AcLDL)-induc ed cholesterol esterification in MPM from BALB/c, Swiss, and DBA/2 strains but had no effect on MPM from C57BL/6 mice. Sequencing of SR-A cDNA from C5 7BL/6 mice demonstrated complete identity with published sequence in the co llagenlike domain. However, four single-residue substitutions were noted in the alpha-helical coiled-coil domain, Site-directed mutagenesis demonstrat ed that a single substitution (L168S) in this domain accounted for the loss of 2F8 immunoreactivity. Differing reactivities toward a commonly used mon oclonal antibody were used to identify polymorphism of SR-A in C57BL/6 mice .