Constant Region Of Heavy Chain Research Articles

Susceptibility to Plasmodium falciparum Malaria: Influence of Combined Polymorphisms of IgG3 Gm Allotypes and Fc Gamma Receptors IIA, IIIA, and IIIB.

The binding of immunoglobulin (Ig) to Fc gamma receptors (FcgR) at the immune cell surface is an important step to initiate immunological defense against malaria. However, polymorphisms in receptors and/or constant regions of the IgG heavy chains may modulate this binding. Here, we investigated whether polymorphisms located in FcgR and constant regions of the heavy chain of IgG are associated with susceptibility to P. falciparum malaria. For this purpose, a clinical and parasitological follow-up on malaria was conducted among 656 infants in southern Benin. G3m allotypes (from total IgG3) were determined by a serological method of hemagglutination inhibition. FcgRIIA 131R/H and FcgRIIIA 176F/V genotypes were determined using the TaqMan method and FcgRIIIB NA1/NA2 genotypes were assessed by polymerase chain reaction using allele-specific primers. Association analyses between the number of malaria infections during the follow-up and polymorphisms in IgG G3m allotypes and FcgR were studied independently by zero inflated binomial negative regression. The influence of combinations of G3m allotypes and FcgRIIA/FcgRIIIA/FcgRIIIB polymorphisms on the number of P. falciparum infections, and their potential interaction with environmental exposure to malaria was assessed by using the generalized multifactor dimensionality reduction (GMDR) method. Results showed that individual carriage of G3m24 single allotype and of G3m5,6,10,11,13,14,24 phenotype was independently associated with a high risk of malaria infection. A risk effect for G3m6 was observed only under high environmental exposure. FcgRIIIA 176VV single genotype and combined carriage of FcgRIIA 131RH/FcgRIIIA 176VV/FcgRIIIB NA1NA2, FcgRIIA 131HH/FcgRIIIA 176FF/FcgRIIIB NA1NA1, FcgRIIA 131HH/FcgRIIIA 176VV/FcgRIIIB NA2NA2 and FcgRIIA 131HH/FcgRIIIA 176VV/FcgRIIIB NA1NA2 genotypes were related to a high number of malaria infections. The risk was accentuated for FcgRIIIA 176VV when considering the influence of environmental exposure to malaria. Finally, the GMDR analysis including environmental exposure showed strengthened associations with a malaria risk when FcgRIIA/FcgRIIIA/FcgRIIIB genotypes were combined to G3m5,6,11,24 and G3m5,6,10,11,13,15,24 phenotypes or G3m10 and G3m13 single allotypes. Our results highlight the relevance of studying IgG heavy chain and FcgR polymorphisms, independently as well as in combination, in relation to the individual susceptibility to P. falciparum infection. The intensity of individual exposure to mosquito bites was demonstrated to impact the relationships found.

The Presence of IGHG1 in Human Pancreatic Carcinomas Is Associated With Immune Evasion Mechanisms

To investigate the expression of Igγ-1 chain C region (IGHG1) in human pancreatic carcinomas and determine the biological function of IGHG1 expression in immune evasion mechanisms. Comparative proteomic analysis was used to detect the differential expression of IGHG1 in human pancreatic cancer tissues versus adjacent noncancerous tissues, followed by confirmatory tests including quantitative real-time reverse transcription-polymerase chain reaction, Western blot analysis, immunohistochemistry, and immunofluorescence. A murine pancreatic tumor model was established by transplantation of IGHG1-overexpressing Panc02 cells. The cytotoxic responses of natural killer (NK) cells were assessed with a lactate dehydrogenase release assay. Igγ-1 chain C region was found to be present in human pancreatic cancer tissues but nearly absent or expressed lower in adjacent noncancerous tissues. In the murine pancreatic tumor model, the tumor growth was significantly accelerated from day 12 to 20 after tumor injection, and the survival time of animals was decreased. Blockage of IGHG1 led to retarded tumor growth and improved survival. The cytotoxicity assay revealed that IGHG1 downregulated the cytotoxic activity of NK cells through inhibition of antibody-dependent cellular cytotoxicity function. The presence of IGHG1 in pancreatic cancer cells might constitute an important element responsible for tumor cell proliferation and immune evasion mechanisms.

The transcription factor BATF controls the global regulators of class-switch recombination in both B cells and T cells

The transcription factor Batf controls TH17 differentiation by regulating the expression of both RORγt and RORγt target genes such as Il17. Here, we report the mechanism by which Batf controls in vivo class switch recombination (CSR). In T cells, Batf directly controls expression of the transcription factors Bcl-6 and c-Maf, both of which are needed for development of T follicular helper (TFH) cells. Restoring TFH activity to Batf−/− T cells in vivo requires co-expression of both Bcl-6 and c-Maf. In B cells, Batf directly controls the expression of both activation-induced cytidine deaminase (AID) and of IH-CH germline transcripts. Thus, Batf functions at multiple hierarchical levels across two cell types to globally regulate in vivo switched antibody responses.

Chimeric proteins comprising the constant region of immunoglobulins for treating hemophilia B (WO2005001025)

The application (WO2005001025) details recombinant fusion proteins attached to the constant region of heavy chains of immunoglobulins. They are found to be particularly useful for the treatment of hemostatic disorders, such as hemophilia B. It aims at engineering chimeric proteins comprising of a single molecule of human factor IX (FIX) and the constant region (Fc domain) of one or two heavy chain(s) of human IgG (rFIXFc). cDNA for rFIXFc was generated by a PCR. rFIXFc protein was isolated and purified from stably transfected mammalian cells. The concentration and clotting activity of rFIXFc were assessed in mice, rats, monkeys, and FIX-deficient mice and dogs, after intravenous administration. The half-life of rFIXFc activity is prolonged by three to fourfold, compared with rFIX, when administered intravenously in all animals. The generation of chimeric proteins, comprised of FIX fused to the Fc domain of IgG, extends the clotting activity of the recombinant molecule. rFIXFc represents a promising candidate for the treatment of patients with hemophilia B. The application claims the methods of making recombinant chimeric proteins comprising of one biologically active molecule fused to the Fc region of the heavy chain(s) of immunoglobulins and their use for therapy.

Immunosuppression by Fc region‐mismatched anti‐T cell antibody treatment

Formation of anti-antibodies (anti-Ab) is known to counteract immunotherapy with anti-T cell antibodies. Our previously described immunological approach prevented anti-Ab with the consequence of prolonged survival of fully mismatched skin grafts in C57BL/6 mice. These mice were treated with a single priming injection of a monoclonal anti-T cell Ab followed by repeated injections of anti-T cell mAb differing in species origin from the priming mAb. We now show prolonged tolerance to discordant xenogeneic, to bispecific, and even to polyclonal Ab, and demonstrate that the underlying immunosuppressive principle is due to a difference in heavy chain constant region between first and second antibodies, independent of whether or not they share the same idiotype. To examine this phenomenon, a panel of mAb was generated which share the same mouse anti-Thy-1.2 idiotype, but carry a human IgG1(T23), IgG3(T212C8), or mouse IgG2a(MmT1) constant heavy chain region. We found that sequential injection of MmT1 and T23 according to the above treatment schedule induced huIgG1 isotype-specific tolerance to T23, which was similar to that seen when using a primary mAb (MmT5) that was, instead, fully mismatched with T23 in both idiotype and constant region. Thus, differences of idiotype between primary and booster Ab were inconsequential for their ability to inhibit anti-Ab formation. This novel form of induced specific tolerance to anti-T cell Ig survived graft rejection and was still evident 230 days after termination of the T cell depletion protocol. Taken together, these results demonstrate that rechallenge with Fc region-mismatched Ab opens an immunological window that allows for induction of tolerance to immunogenic anti-T cell Ab and prolonged immunosuppression.

Successive switching of antibody isotypes expressed within the lines of a B-cell clone.

An antigen-stimulated B cell can differentiate to form a clone of cells that secrete antibodies with the IgM, IgG1, and IgA isotypes. We have examined the sequence of isotype expression by proliferating cell lines within a clone by directly staining for immunoglobulin in the cytoplasm of clonal daughter cells. All of the cones selected for analysis originally secreted IgM as well as other isotypes, as determined by radioimmunoassay of culture fluids. Cell staining showed that (i) at least 25% of the cells contained more than one isotype, indicating that cells can switch expression of isotypes during clonal expansion; (ii) some cells contained both IgM and IgA without detectable IgG1, and some cells contained both IgM and IgG1 without detectable IgA, suggesting that cells can switch from IgM directly to IgG1 or IgA; and (iii) some cells contained both IgG1 and IgA, indicating that cell lines can undergo two successive switches from IgM to the IgG1 and IgA isotypes. Using serological markers for allotypic determinants on the constant region of heavy chains, we have also shown that heterozygous B cells specific for phosphorylcholine generated clones of cells that secreted IgG1 and IgA antibodies that were derived from the expression of genes on only one parental chromosome. Assuming that the gene coding for the IgA isotype is the last gene in the gene cluster coding for heavy chain isotypes, we have proposed a model of successive, but not necessarily stepwise, switching of isotypes within B-cell lines, leading to the eventual accumulation of cells expressing IgA.

Opinion

Abstract In 1965, the “two gene-one polypeptide” theory for the synthesis of antibody chains was first proposed (1). Since then, amino acid sequence studies and genetic analyses of the variable (V)2 and constant (C) regions of light (L) and heavy (H) chains have been consistent with this hypothesis (2). A direct demonstration of the existence of separate genetic units was achieved in 1977 (3), when it was shown that the DNA segments (exon DNA) coding for V and C regions of mouse L chains (λ type) are separated from one another by a large DNA segment (intron or intervening sequence or IVS) that is missing from the mRNA that serves as the template for the L chain. In addition, in DNA derived from embryonic cells, the V gene is shorter than expected (4, 5), ending at the codon specifying position 98 instead of 112 commonly accepted at the VC joining region.

Evidence for the linkage of the IGC H locus to a gene controlling the idiotypic specificity of anti-p-azophenylarsonate antibodies in strain A mice.

Anti-p-azophenylarsonate (anti-Ar) antibodies elicited in all strain A/J mice tested share one or more idiotypic specificities. These specificities are also found in the anti-Ar antibodies of mice of the closely related strain, AL/N, but not in those of BALB/c mice. Anti-Ar antibodies were elicited in congenic mice in which the IgC(H) locus of AL/N mice, which controls allotypic markers in the constant regions of heavy chains, had been introgressively backcrossed for nine generations onto a BALB/c background; the mice were then rendered homozygous for the AL/N allotypic determinant. On the average, these antibodies were quantitatively equivalent, with respect to content of the cross-reactive idiotype, to those of AL/N mice. This indicates that the gene controlling the idiotype is closely linked to the IgC(H) locus. Since idiotype must be a function of V region sequences, the results suggest close linkage of V(H) and C(H) genes. The cross-reactive idiotype was found in nearly all F(1) mice (C57/BL x A/J or BALB/c x A/J) tested.