Interferon-induced expression of class II major histocompatibility antigens in the major histocompatibility complex (MHC) class II deficiency syndrome

Class II antigens encoded by genes of the major histocompatibility complex (MHC) are expressed by a variety of cell types and have a vital role in the cellular interactions required for an effective immune response. We have analyzed the regulation of HLA-DR, DP, and DQ class II antigen expression on cells of different lineage from an immunodeficient patient with the MHC class II deficiency syndrome. T and B lymphocytes, monocytes, and fibroblasts, which initially expressed no class II antigens, were treated with inductive stimuli that normally lead to enhanced expression of class II antigens. Monocytes, but not fibroblasts, cultured for 48–96 hr in the presence of recombinant gamma interferon expressed all three types of class II antigens. In contrast, T lymphocytes did not express class II antigens following their exposure to a variety of stimuli, including activation with phytohemagglutinin and culture in the presence of interleukin-2, transformation by the retrovirus HTLV-1 or HTLV-2, or exposure to the demethylating agent 5-azacytidine. Similarly, class II antigens were not induced on B cells by cross-linkage of surface immunoglobulin molecules with anti-mu, exposure to Epstein-Barr virus, or treatment with soluble factors secreted by activated T cells. These results demonstrate that the regulation of class II MHC antigen expression by monocytes and lymphocytes is dissimilar and suggest that different regulatory genes are involved in the control of class II antigen expression by cells of different lineage.     

Changes in expression of class II antigens of the major histocompatibility complex induced by interferon preparations studied by ELISA

Institute of Immunology, Ministry of Health of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 108, No. 11, pp. 577–580, November, 1989.     

Monoclonal antibodies to human major histocompatibility complex class II antigens

The production and characterization of monoclonal antibodies to major histocompatibility complex (MHC) class II molecules have contributed significantly to delineating the number and structure of gene products of the D region of HLA. The "first generation" of class II monoclonal antibodies detected monomorphic determinants, often reacting with multiple class II loci gene products. Later generations of anti-class II monoclonal detected serologic specificities like those previously detected by human alloantisera. In addition, numerous antibodies have been generated against polymorphic HLA class II determinants which have not been previously described using human allosera. Biochemical analysis utilizing techniques such as radiolabeling and immunoprecipitation, one- and two-dimensional gel electrophoresis, Western blotting, limited N-terminal amino acid sequencing, and peptide mapping have localized the epitopes detected by polymorphic anti-class II monoclonals to various class II locus gene products. Such analyses with monoclonal antibodies have also identified class II gene products previously identified only with cellular reagents. The fact that several monoclonal antibodies with similar serologic specificity detect different class II locus gene products underscores the complexity of the HLA-D region and suggests some possible mechanisms for the generation of polymorphisms in this region.     

Transfection of major histocompatibility complex class I and class II genes causes tumour rejection

Many human and mouse tumours do not express MHC class II antigens and have reduced levels of class I antigens. Because of the requirement for class I and/or class II antigen for antigen presentation to Th and Tc cells, these phenotypes may enable tumour cells to 'escape' the host's immune response. Experiments presented here are designed to assess the role of MHC class I and class II antigens in tumour immunity, and to overcome the MHC class I- or class II-negative phenotype. When transfected with the syngeneic H-2Db gene, the MHC antigen-negative 402AX teratocarcinoma expresses high levels of H-2Db antigen. 402AX/Db cells are rejected by MHC allogeneic and some MHC syngeneic 402AX-susceptible mice, however the fully syngeneic strain of origin (129) remains tumour-susceptible. Induction of MHC class I gene products on class I antigen-negative embryonal carcinoma cells therefore increases tumour immunogenicity in some hosts, but not in the fully syngeneic mouse. In an attempt to enhance antigen presentation of tumour-associated antigens to Th cells, MHC class I antigen-positive SaI (KkDd) sarcoma cells were transfected with syngeneic A alpha k and A beta k genes to generate Iak-expressing tumour cells. SaI/Ak cells are efficiently rejected by syngeneic A/J (KkDd) mice, while untransfected SaI cells are lethal. Induction of MHC class II antigen expression on the class I antigen-positive SaI sarcoma therefore completely abrogates malignancy.     

T cell recognition of donor major histocompatibility complex class I peptides during allograft rejection.

LEW (RTI1) recipients of DA (RTIav1) skin and kidney allografts were tested for the capacity of their T lymphocytes to proliferate to three 22-24-amino acid peptides from the hypervariable regions of the RTI-Aav1 classical MHC class I molecule. Ten days after rejecting second-set DA kidney allografts, spleen cells (but interestingly not lymph node cells) from LEW recipients showed strong, LEW antigen-presenting cell-dependent, CD4+ T cell proliferation to peptide 1 (from the alpha helical region of the alpha 1 domain). CD8+ T cells showed no response to peptide 1. There was no response by the spleen cells to peptide 2 (from the beta sheet of the alpha 2 domain) or peptide 3 (from the alpha helical region of the alpha 2 domain). Immunization of LEW rats with pure RTI-Aav1 class I H chain in Freund's adjuvant gave responses identical to that seen after grafting, i.e. good CD4+ T cell proliferation to peptide 1, but none to peptides 2 and 3. However, immunization of LEW rats with peptides 1, 2 and 3 in Freund's adjuvant resulted in good CD4+ T cell proliferation responses to each of the peptides. These data demonstrate that indirect allorecognition can be stimulated by allograft rejection, and emphasize that the physiological processing of donor antigens will influence which peptides will be important in indirect allorecognition in transplantation.     

Soluble major histocompatibility complex molecules in immune regulation: highlighting class II antigens

The involvement of major histocompatibility complex (MHC) antigens in the development and regulation of immune response has been well defined over the years, starting from maturation, antigenic peptide loading, migration to the cell membrane for recognition by the T‐cell receptor and recycling for immune response cessation. During this intracellular trafficking, MHC antigens find a way to be excreted by the cells, because they can be found as soluble MHC class I (sMHC‐I) and class II (sMHC‐II) molecules in all body fluids. Although secretion mechanisms have not been sufficiently studied, sMHC molecules have been shown to display important immunoregulatory properties. Their levels in the serum have been shown to be altered in a variety of diseases, including viral infections, inflammation, autoimmunities and cancer, etc. while they seem to be involved in a number of physiological reactions, including maintenance of tolerance, reproduction, as well as mate choice vis‐à‐vis species evolution. The present review aims to present the thus far existing literature on sMHC molecules and point out the importance of these molecules in the maintenance of immune homeostasis.     

Treatment of autoimmune diseases with antibodies to class II major histocompatibility complex antigens

The family of Fc receptors (FcR) for IgG play pivotal roles in affector, effector, and regulatory functions of cells of the immune system. Thus, changes in expression and activation of FcRs may contribute to a variety of disease manifestations that are the consequence of abnormalities in immune system function. Patients with diabetes mellitus are often plagued with recurrent bacterial and mycotic infections, as well as large and small vessel injury which may in part be immune mediated and which lead to organ dysfunction. Hormone-mediated changes in immune system function have been postulated to contribute to a variety of the complications experienced by patients with diabetes mellitus. It is the purpose of this review to summarize current knowledge regarding abnormalities in immune system function in diabetes mellitus with special emphasis on classical hormonal modulation of Fc receptor-mediated phagocytosis.     

Expression of major histocompatibility complex class II antigens on normal porcine intestinal endothelium

A novel monoclonal antibody (MIL 11) specific for an antigen expressed on porcine endothelial cells is described. The antigen recognized by MIL 11 is most strongly expressed in the intestine but is also expressed on the capillary endothelium of a wide range of tissues. Using two- and three-colour immunofluorescence microscopy we demonstrated the extensive coexpression of MIL 11 and major histocompatibility complex (MHC) class II antigens on normal porcine capillary endothelium in the intestine, trachea, thymus and small veins, while endothelium of large vessels and the heart were negative for MHC class II. In contrast to humans and rodents, available reagents do not detect MHC class II on the intestinal epithlium of pigs. However, porcine intestinal endothelium expressed both DR and DQ antigens. A population of strongly class II-positive cells was also detected immediately adjacent to the endothelium in the lamina propria. Three-colour immunofluorescence microscopy highlighted the close association between endothelium and intestinal CD4⁺ T cells. Lamina propria T cells were mainly MHC class II positive, whereas those in the epithelial compartment were MHC class II negative.     

Molecular analysis of the genes for human class II antigens of the major histocompatibility complex

Different cDNA clones have been isolated that encode each of the three chains of HLA-DR antigens: alpha, intermediate and beta, as well as another beta chain, most likely DC. Whereas the DR alpha and intermediate chains seem encoded by single genes, the DR and DC beta chains are most likely encoded by multiple genes; furthermore, their polymorphism can be readily detected by restriction analysis of cellular DNA. Several genomic DNA clones were isolated for the DR and DC beta chain genes and for the intermediate chain gene. The sum of all distinct cDNA clones and genomic DNA clones for HLA-DR beta chains, isolated from a heterozygous cell line, represent five genes. This implies the existence of at least three nonallelic DR beta chain genes in addition to the DC beta chain genes. The complete sequence of one of the DR beta chains is presented. A genomic DNA clone for a DR beta chain was transferred into mouse L cells and found to be expressed into RNA of the same size as DR beta mRNA. The finding, among the genes for class II antigens, of multiple genes for the beta chain of HLA-DR, distinct from those of other known subregions such as DC, emphasizes the importance of gene transfer experiments, where individual genes can be expressed and tested for their functional role in the immune response.     

Vaccination induces major histocompatibility complex class II expression in the Atlantic salmon eye

The aim of the study was to investigate the presence, distribution and density of major histocompatibility complex (MHC) class II+ cells in the ocular tissues of the Atlantic salmon, Salmo salar, prior to and following vaccination. Eyes were collected 14 days prior to and at 4, 11, 25 and 39 days and 4 months subsequent to vaccination with a commercial fish vaccine. A quantitative analysis was performed in sections on the number of immunopositive cells in the retinal layers. In all groups, MHC class II+ cells were detected in the area of the limbus but not in the central parts of the cornea. In the uvea, immunopositive cells were present in unvaccinated and vaccinated fish. Abundant immunopositive cells were identified in the choroid rete (or choroid gland) in all groups as well as in the ventral ciliary cleft, where macrophage-like MHC class II+ cells were seen. Quantitative histology of the retina revealed a significant increase in MHC class II+ cells in the outer plexiform layer (OPL) and the inner nuclear layer (INL) 4 days following vaccination. Positive cells were detected in all layers of the retina with the exception of the photoreceptor layer.     

Rabbit major histocompatibility complex. IV. Expression of major histocompatibility complex class II genes

The rabbit MHC class II DP, DQ, and DR alpha and beta chain genes were transfected into murine B lymphoma cells. The transfected cells expressed R-DQ and R-DR molecules on the cell surface but they did not express the R-DP genes either on the cell surface or at the level of mRNA. Northern blot analyses showed that the R-DP genes were expressed, albeit at low levels, in rabbit spleen. Similar analyses showed that the R-DQ and R-DR genes were expressed at high levels in rabbit spleen. A new monoclonal anti-rabbit class II antibody, RDR34, has been developed and shown to react with the R-DR transfected cells and not with the R-DQ transfected cells. The previously described monoclonal anti-rabbit class II antibody, 2C4, reacted with the R-DQ transfected cells and not with the R-DR transfected cells. Thus, 2C4 and RDR34 MAb's are specific for the R-DQ and R-DR molecules, respectively. Each of the antibodies reacted with approximately 50% of rabbit spleen cells as shown by immunofluorescent antibody studies.     

Expressed major histocompatibility complex class II loci in fishes

Summary: Peptides derived from parasites are presented to T helper cells by major histocompatibility complex (MHC) class II αβ heterotrimeric cell-surface molecules. In mice and humans, the genes encoding these antigen-presenting molecules are known to be polymorphic and poly-genic. Multiple loci for MHC class II A and E genes are proposed to allow for an increased peptide-binding repertoire. The multigenic nature of expressed MHC class II loci and the differences between these loci in fishes are the focus of this review, Particular emphasis is placed on an evolutionary comparison of class II B loci, especially two class 11 B loci that have undergone dramatic changes from one another suggesting an ancestral gene duplication event that took place at an early stage in the evolution of teleosts, The number of functional class II αβ loci heterotrimers may have a profound impact on the organisms ability to battle constantly evolving parasitic infections.     

Differential major histocompatibility complex class II locus expression on human laryngeal epithelium

The survival of a laryngeal allograft will be dependent on the immunological composition of the donor larynx and, in particular, on the expression of major histocompatibility complex (MHC) class II antigens on professional and non-professional antigen-presenting cells. Laryngeal and tonsillar biopsies from normal individuals aged 18-78 years were processed and prepared for quantitative, multiple-colour immunofluorescence using mouse antihuman monoclonal antibodies to human leucocyte antigen (HLA)-DR, HLA-DQ and CD45. The laryngeal epithelium expressed HLA-DR locus products at variable levels, but expression of HLA-DQ was virtually absent. Tonsillar epithelial cells expressed HLA-DR at the basal layer only, while HLA-DQ was similarly not expressed. In contrast, both HLA-DR and -DQ locus products were present on lamina propria and intraepithelial leucocytes in both laryngeal and tonsillar mucosae, although at varying levels. The finding that laryngeal epithelial cells express MHC class II antigens has implications for the survival of laryngeal allografts and suggests that they may require significant immunomodulation. In addition, antigen presentation by epithelial cells has been hypothesized to contribute to the immunoregulatory function of mucosal tissues, and the finding that HLA-DQ locus products are only expressed at low levels by laryngeal epithelium raises questions about the repertoire of peptides to which the mucosal immune system can respond.     

Processing and major histocompatibility complex class II presentation of Legionella pneumophila antigens by infected macrophages

To better understand interactions between the intracellular pathogen Legionella pneumophila and macrophages (Mphis), host and bacterial determinants important for presentation of antigens on major histocompatibility complex class II molecules (MHC-II) were investigated. It was determined that immune CD4 T-cell responses to murine bone marrow-derived Mphis (BMphis) infected with wild-type L. pneumophila were higher than the responses to avirulent dotA mutant bacteria. Although this enhanced response by immune T cells required modulation of vacuole transport mediated by the Dot/Icm system, it did not require intracellular replication of L. pneumophila. Intracellular cytokine staining identified a population of immune CD4 T cells that produced gamma interferon upon incubation with BMphis infected with wild-type L. pneumophila that did not respond to Mphi infection with dotA mutant bacteria. Endocytic processing was required for presentation of L. pneumophila antigens on MHC-II as determined by a defect in CD4 T-cell responses when the pH of BMphi endosomes was neutralized with chloroquine. Investigation of MHC-II presentation of antigens by BMphis infected with L. pneumophila icmR, icmW, and icmS mutants indicated that these mutants have an intermediate presentation phenotype relative to those of wild-type and dotA mutant bacteria. In addition, it was found that antigens from dot and icm mutants are presented earlier than antigens from wild-type L. pneumophila. Although immune CD4 T-cell responses to proteins secreted by the L. pneumophila Lsp system were not detected, it was found that the Lsp system is important for priming L. pneumophila-specific T cells in vivo. These data indicate that optimal antigen processing and MHC-II presentation to immune CD4 T cells involves synthesis of L. pneumophila proteins in an endoplasmic reticulum-derived compartment followed by transport to lysosomes.     

Decreased anti-donor major histocompatibility complex class I and increased class II alloantibody response in allograft tolerance in adult rats

Permanent tolerance to allografts can be induced in adult rats by donor-specific transfusions (DST) prior to transplantation. We have previously reported, in a model of heart allograft, the presence of a heavy leukocyte infiltrate, in the allograft which displayed a strong allospecific cytotoxicity when tested in vitro against donor cells, and a strong accumulation of mRNA for granzyme A and perforin in vivo. In contrast, there was a major decrease in the accumulation of mRNA for interleukin-2 and interferon-γ. These results suggested that the DST-induced tolerance was associated with a decrease in type-1 T helper (Th1) cell function. The major role of preformed antibodies in xeno and allorejection is clearly established. Nevertheless, the consequences of alloantibody production in acute rejection and tolerance induction remains to be elucidated. We here analyze the alloantibody response in rejecting and DST-treated recipients. We show that, after transplantation, tolerant recipients, in contrast to rejecting ones, mount a low IgM alloresponse that switches to low IgG production. Detailed analysis of IgG alloantibodies in DST-treated recipients revealed that their production decrease was not equally distributed. Whereas rejecting animals mounted a strong anti-class I and II IgG alloantibody response, DST-treated recipients produced anti-class II and low titers of anti-class I IgG alloantibodies. Furthermore, among IgG subclasses, tolerant recipients predominantly produced IgG2a, a profile which, in the rat, is compatible with a Th2-controlled response. Finally, the passive transfer of immune serum from rejecting animals to DST-treated recipients could abrogate the tolerance. We suggest that the absence of anti-class I alloantibodies combined with preserved and/or increased anti-class II production plays a major role in graft tolerance in this model. These results reinforced the role of alloantibodies in rejection and in induction of tolerance.     

Expression of class II major histocompatibility complex antigens on adult T cells in Xenopus is metamorphosis-dependent

Class II major histocompatibility complex (MHC) antigens are expressed predominantly on B lymphocytes and macrophages of tadpoles of the South African clawed frog, Xenopus laevis, as is the pattern in lymphocyte populations of most mammals. However, unlike most mammals, young postmetamorphic frogs show expression of class II MHC antigens on a high proportion of thymocytes and most peripheral T and B lymphocytes. Using the J-strain of Xenopus and the anticlass II monoclonal antibody, 14A2, we have studied, by indirect immunofluorescence, whether inhibition of metamorphosis would alter the pattern of expression of class II antigens during ontogeny. In control animals, class II antigens were virtually absent from thymic lymphocytes and peripheral T cells of normal untreated larvae, but could be found in increasing numbers in both populations after metamorphosis (10-12 weeks of age). In contrast, larvae, whose metamorphosis was inhibited by treatment with sodium perchlorate, had relatively few class II+ thymic lymphocytes throughout the 6-month period of study, and the proportion of class II+ splenic lymphocytes was approximately equal to that of IgM+ B lymphocytes. Thus, perchlorate-treated animals retained the larval pattern of class II expression, suggesting that emergence of class II+ T cells is dependent on metamorphosis.