Papain cleavage of rabbit secretory immunoglobulin A. Differential sensitivity of f and g subclasses

Abstract

Rabbit secretory immunoglobulin A (sIgA) was digested with papain in the absence of reducing agent and four fractions were isolated by gel filtration. Three of the four fractions, undigested sIgA, Fc~,, and Fabz, have previously been characterized (Hanly et ai. (1973), Biochemistry 12, 733); the fourth fraction (approximately 15% of the total protein) was identified as Fab,-like material by its sedimentation and antigenic properties. Each of the four fractions was analyzed for the allotypic specificities controlled by the f and g loci by quantitative precipitation of the radiolabeled fractions with anti-f or anti-g antisera. The f allotypic specificities

Recombinant Rabbit Secretory Immunoglobulin Molecules: Alpha Chains with Maternal (Paternal) Variable-Region Allotypes and Paternal (Maternal) Constant-Region Allotypes

“…The Cag locus controls allotypic specificities on the constant region of alpha heavy chains (on both the Fc and Fd portions), and the VHa locus controls allotypic specificities on the variable region of the alpha chain (2,8,9). If no recombinant IgA molecules exist, rabbits heterozygous at the VHa and Cag loci would be expected to have only two types of IgA molecules (with respect to these two loci).…”

“…The g locus controls the allotypic specificities g74 and g75 on the constant part of alpha chains of a second subclass of IgA (8,9). The g74 and g75 allotypic specificities are each comprised of multiple antigenic determinants, some of which are present on the The phenomenon of allelic exclusion (11), in which only one of the two alleles at a given locus is expressed, exists for several immunoglobulin loci at the molecular and cellular levels (11)(12)(13)(14).…”

Differential Susceptibility of Human IgA Immunoglobulins to Streptococcal IgA Protease

“…Knight, Lichter, and Hanly (22) have reported detailed studies on secretory IgA of the rabbit, showing that molecules bearing the g genetic allotype are susceptible to papain cleavage, while those of the f allotype are highly resistant. Differences in susceptibility to proteases have also been found among human IgG subclasses (23).…”

Mesenteric lymph node B lymphoblasts which home to the small intestine are precommitted to IgA synthesis.

“…Jones et al (19), using a fluorescence-activated cell sorter, demonstrated that the precursor cells in Peyer's patches bear surface K-, but not it-chains. Subsequently, the tLminus, K-positive population, which contains the precursors of the IgA-producing plasma cells, was shown to contain a-positive cells detectable with antisera to IgA allotypes (20,21). However, the precursor cells have not directly been shown in transfer experiments to bear surface a-chains.…”