Serum immunoglobulin levels and naturally occurring antibodies against carbohydrate antigens in germ‐free BALB/c mice fed chemically defined ultrafiltered diet

Abstract

This study investigates the influence of exogenous antigenic stimulation on the serum immunoglobulin levels and the levels of circulating natural antibodies against carbohydrate antigens. Thus, BALB/c mice, raised in a germ-free environment and fed a chemically defined, ultrafiltered diet (GF-CD), were employed. These mice had normal serum IgM levels, but IgG and IgA levels were approximately 5% of conventionally reared littermates. The concentrations of all four IgG isotypes were equally low. The variable part of the heavy chains of naturally occurring BALB/c antibodies against a number of carbohydrate antigens, including 3-fucosyllactosamine (3-FL), levan and dextran, are encoded by VH441, and these antibodies express cross-reactive idiotopes recognized by the monoclonal antibodies 6C4 and 6B1. Antibodies against levan and dextran were lower in GF-CD than in conventional mice, but levels of anti-3FL antibodies, and 6C4 and 6B1 idiotopes, were comparable to those in conventional animals. Peptidoglycan polysaccharide complexes (PPC) are carbohydrate antigens of bacterial origin, like levan and galactan. Naturally occurring antibodies against PPC were found in the serum of conventional mice, but were severely reduced in GF-CD mice. The results indicate that most naturally occurring antibodies against carbohydrate antigens of bacterial origin found in conventional mice are caused by exogenous stimulation.

Mice Deficient in Complement Receptors 1 and 2 Lack a Tissue Injury-Inducing Subset of the Natural Antibody Repertoire

“…In support of the concept that B-1 B cells generate this subset is the extensive previous analysis of these cells demonstrating that they produce a large repertoire of low-affinity self-reactive Abs that result from positive selection during B-1 cell development (14,(42)(43)(44). If CR2/CR1 coreceptor function on B-1 B cells is required for the efficient recognition of a critical self Ag that is either identical to, or antigenically related to, the neoantigen revealed on ischemic tissue, this could, in principle, explain our findings relative to the lack of development of this subset of Abs.…”

Expression of Retinaldehyde Dehydrogenase Enzymes in Mucosal Dendritic Cells and Gut-Draining Lymph Node Stromal Cells Is Controlled by Dietary Vitamin A

“…Germ-free mice show reduced numbers of lamina propria CD4 + T cells, IgA-producing B cells, and intraepithelial lymphocytes (55,56), and MLNs and spleens are smaller and less cellular (57). This indicates that commensal bacteria play a crucial role in the maturation of the mucosal immune system during postnatal development.…”

Marginal zone B cells are naturally reactive to collagen type II and are involved in the initiation of the immune response in collagen-induced arthritis

“…In agreement, natural Abs are independent of internal or external stimuli, whereas genetic differences seem to influence their titres. 33,34 show for example spontaneous reactivity to double-stranded DNA, a self-Ag in murine lupus. 15,36,37 Indeed, when we separated the splenic B cells from naive DBA/1 mice into FO and MZ B cells, we found that the majority of IgG anti-CII AFCs belonged to the MZ B-cell population, and after CII immunization the MZ B cells were the first to significantly expand.…”