Monoclonal Antibodies Specific for Rat IgG1,IgG2a,and IgG2b Subclasses,and Kappa Chain Monotypic and Allotypic Determinants: Reagents for Use with Rat Monoclonal Antibodies

ABSTRACT

Mouse monoclonal antibodies to rat IgG were obtained by fusion of immune SJL mouse spleen cells to NSI myeloma cells. Seven monoclonal antibodies have been labeled with ¹²⁵I and studied as to specificity and avidity by using a panel of rat monoclonal antibodies both as inhibitors and target antigens in soft well plate and indirect cell binding assays. All MAb were selected for high avidity of 4 × 10⁷ to ≥ 2 × 10⁹ M⁻¹. Four MAb were subclassspecific. RG11/39, RG7/1, and RG7/11 were absolutely specific for the Fc' region of IgGl, IgG2a, and IgG2b, respectively. RG9/6 showed specificity for the Fab' region of IgG2a but crossreacted with lower avidity with IgG2c. Three MAb reacted with rat kappa chains. RG7/9 defined a monotypic (common) kappa chain determinant. RG11/15 and RG7/7 were specific for allelic kappa la and kappa lb determinants, respectively. The monotypic and kappa la allotypic determinants are topographically separated. The antibodies can be used as screening reagents in indirect cell binding assays. They have sensitivity similar to affinity-purified rabbit anti-rat IgG and more defined specificity. They do not crossreact with mouse or human IgG, making them particularly suitable companion reagents for rat anti-mouse or anti-human MAb. One Mab, RG7/7, strongly crossreacts with Syrian hamster IgG.