Antigen processing and presentation to T cells

Bacillus Calmette-Guérin (BCG) vaccine generates immunoregulatory cells in the cervical lymph nodes in guinea pigs injected intra dermally

This work demonstrates the presence of immune regulatory cells in the cervical lymph nodes draining Bacillus Calmette-Guérin (BCG) vaccinated site on the dorsum of the ear in guinea pigs. It is shown that whole cervical lymph node cells did not proliferate in vitro in the presence of soluble mycobacterial antigens (PPD or leprosin) despite being responsive to whole mycobacteria. Besides, T cells from these lymph nodes separated as a non-adherent fraction on a nylon wool column, proliferated to PPD in the presence of autologous antigen presenting cells. Interestingly, addition of as low as 20% nylon wool adherent cells to these, sharply decreased the proliferation by 83%. Looking into what cells in the adherent fraction suppressed the proliferation, it was found that neither the T cell nor the macrophage enriched cell fractions of this population individually showed suppressive effect, indicating that their co-presence was necessary for the suppression. Since BCG induced granulomas resolve much faster than granulomas induced by other mycobacteria such as Mycobacterium leprae the present experimental findings add to the existing evidence that intradermal BCG vaccination influences subsequent immune responses in the host and may further stress upon its beneficial role seen in Covid-19 patients.

Mechanism of Action of Antimalarial Drugs: Inhibition of Antigen Processing and Presentation

Recent studies have elucidated the steps involved in the association of antigenic peptides with major histocompatibility complex (MHC) encoded proteins and have suggested how antimalarial compounds might influence this important site of immune activation. These steps of antigen presentation in the macrophage (or other antigen-presenting cells) include: (a) the partial proteolytic degradation of endogenous and exogenous proteins into peptides within the lysosome; (b) the synthesis of MHC class II (i.e. HLA-D associated) α, β, and invariant (Ii) chains in the endoplasmic reticulum; (c) the initial association of α-Ii and β-li chains in the endoplasmic reticulum and the transport of these complexes to the primary endosome; (d) the fusion of lysosomal vacuoles and endosomal vacuoles, allowing the mixtures of lysosomal enzymes, peptides, α–Ii and β–Ii; (e) the displacement of Ii chains by peptides to form α–β–peptide complexes in the endosome; and (f) the migration of α–β–peptide complexes to the macrophage cell surface where they can stimulate CD4 T cells, resulting in release of cytokines. A low pH is required for digestion of the protein by acidic hydrolases in the lysosome, for assembly of the α–β–peptide complex and for its transport to the cell surface. Chloroquine and hydroxychloroquine are weak diprotic bases that can diffuse across the cell membrane and raise the pH within cell vesicles. This background provides the underlying basis for the theory that antimalarials may act to prevent autoimmunity by the following putative mechanism. Antimalarial compounds may: (a) stabilize the α-Ii and β-Ii interactions and prevent low-affinity peptides from forming α–β–peptide complexes; and (b) interfere with the efficient movement of α-Ii, β-Ii and α–β–peptide complexes to the correct locations within the cell cytoplasm or to the cell surfaces. Decreased presentation of autoantigenic peptides by macrophages might then lead to downregulation of autoimmune CD4+ T cells and diminish release of cytokines associated with clinical and laboratory signs of autoimmune disease.

Beyond the classical: influenza virus and the elucidation of alternative MHC class II-restricted antigen processing pathways

CD4+ T cells (T(CD4+)) are activated by peptides, generally 13-17 amino acids in length, presented at the cell surface in combination with highly polymorphic MHC class II molecules. According to the classical model, these peptides are generated by endosomal digestion of internalized antigen and loaded onto MHC class II molecules in the late endosome. Historically, this "exogenous" pathway has been defined through the extensive use of purified proteins. However, the relatively recent use of clinically relevant antigens, those of influenza virus in our case, has revealed several additional pathways of peptide production, including some that are truly "endogenous", entailing synthesis of the protein within the infected cell. Indeed, some peptides appear to be created only via endogenous processing. The cell biology that underlies these alternative pathways remains poorly understood as do their relative contributions to defence against infectious agents and cancer, and the triggering of autoimmune diseases.

Molecular analysis of thymopentin binding to HLA-DR molecules

Thymopentin (TP5) triggers an immune response by contacting with T cells; however the molecular basis of how TP5 achieves this process remains incompletely understood. According to the main idea of immunomodulation, we suppose that it would be necessary for TP5 to form complex with human class II major histocompatibility complex DR molecules (HLA-DR) before TP5 interacts with T cells. The uptake of TP5 by EBV-transformed B cells expressing HLA-DR molecules and the histogram of fluorescence intensities were observed by using fluorescent- labeled TP5, testifying the direct binding of TP5 to HLA-DR. The binding specificity was confirmed by the inhibition with unlabeled TP5, suggesting the recognition of TP5 by HLA-DR. To confirm the interaction between TP5 and HLA-DR, the complex formation was predicted by using various modeling strategies including six groups of trials with different parameters, alanine substitutions of TP5, and the mutants of HLA-DR. The results demonstrated that TP5 and its alanine substitutions assumed distinct conformations when they bound to HLA-DR. The observation further showed that there was flexibility in how the peptide bound within the binding cleft. Also, the molecular analysis supplemented a newly important discovery to the effect of Val anchor on TP5 binding HLA-DR, and revealed the important effects of Glu11 and Asn62 on the recognition of TP5. These results demonstrated the capability of TP5 to associate with HLA-DR in living antigen presenting cells (APC), thereby providing a new and promising strategy to understand the immunomodulation mechanism induced by TP5 and to design potential immunoregulatory polypeptides.

Antimalarial drugs in systemic lupus erythematosus: use in pregnancy

The 4-aminoquinoline radical containing antimalarial drugs are also used in the management of various connective tissue diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis. These agents are particularly useful for the management of inflammatory polyarthritis and skin disease. By raising the pH in intracellular compartments, these drugs interfere with normal phagocytic function which consequently enables them to interfere with antigen processing. Other actions include inhibition of platelet aggregation, this is advantageous in patients with phospholipid antibodies (aPL) which are known to predispose patients to recurrent arterial and venous clinical thrombotic events. Hydroxychloroquine has also been demonstrated to reduce serum lipid levels including cholesterol, triglycerides and low density lipoproteins. As it is now known that patients with SLE are at risk for accelerated artherogenesis and premature heart disease, this action may be an added benefit for these patients. The use of the 4-aminoquinoline radical containing antimalarial drugs during pregnancy is controversial. It is known that these agents can cross the placenta and are deposited in fetal pigmented tissues. These findings have led to the recommendation that these agents should be discontinued in pregnancy for patients with connective tissue diseases even though they have long been recommended for malarial prophylaxis in pregnant women travelling to malarial infested areas. Flares of SLE disease have been documented when these agents are discontinued and as flares of SLE disease activity are known to be detrimental to pregnancy outcome in patients with SLE, it is our opinion that these drugs should not be discontinued during pregnancy in a patient with lupus, particularly when the known terminal elimination half life is 1 to 2 months.

Protection from IBDV-induced bursal damage by a recombinant fowlpox vaccine, fpIBD1, is dependent on the titre of challenge virus and chicken genotype

Expression of the VP2 capsid protein of infectious bursal disease virus (IBDV) in an vaccine strain of fowlpox has produced an experimental recombinant vaccine, fpIBD1. Successful vaccination with fpIBD1 was dependent on the titre of challenge virus for high titres of challenge virus were able to overcome protection induced by fpIBD1 whereas challenge with a low titre of virus did not. The genotype of chicken also has an important effect on the outcome of challenge possibly as a result of the major histocompatability complex and its ability to present VP2-derived peptides to the immune system. It was not possible to protect the inbred white leghorn chicken strain, line 15I, from IBDV-induced bursal damage by vaccination with fpIBD1 even at the lowest titre of challenge virus used. All other inbred white leghorn chickens examined (line 6(1), C. B4 and C.B12) and outbred Rhode Island Red chickens were protected by fpIBD1. Protection by the fpIBD1 vaccine is induced in the absence of detectable serum antibodies, suggesting the possibility of a significant role for cell-mediated immunity in protection from IBDV challenge.

Induction of apoptosis in peripheral blood lymphocytes following treatment in vitro with hydroxychloroquine

OBJECTIVE

Defective regulation of apoptosis may be central to the development of autoimmune disorders. This study investigated the possibility that the antirheumatic effect of hydroxycholoroquine (HCQ) may be achieved by up-regulation of apoptosis.

METHODS

Peripheral blood lymphocytes collected from normal controls and patients with systemic lupus erythematosus (SLE) were cultured in the presence or absence of a range of concentrations of HCQ. Cells undergoing apoptosis were identified by several standard methods, including morphologic changes, DNA fragmentation, and flow cytometry. For some experiments, lymphocytes were simultaneously stained with antibodies to T cell surface markers and with propidium iodide for dual-stain flow cytometric studies.

RESULTS

HCQ was able to induce apoptosis in peripheral blood lymphocytes in a dose- and time-dependent manner. HCQ induced these changes in all T cell subpopulations studied. There was no significant difference between the controls and patients with SLE in terms of the percentage of apoptotic cells detected following treatment with HCQ.

CONCLUSION

The present study demonstrated that HCQ induces apoptosis in peripheral blood lymphocytes, which leads to the speculation that HCQ may exert its antirheumatic effect through this mechanism.

Mechanism of enhanced antigen presentation by B cells activated with anti-mu plus interferon-gamma: role of B7-2 in the activation of naive and memory CD4+ T cells

B cells activated with anti-mu antibody plus interferon (IFN)-gamma exerted strong antigen presentation activity for T cell proliferation. The enhanced antigen presentation function was shown to be due to the increase in B7-2 expression. When B cells were stimulated with anti-mu, expression of MHC major histocompatibility complex class II, heat-stable antigen (HSA), ICAM-1 and B7-2 was increased. The presence of IFN-gamma further augmented the expression of B7-2 on anti-mu-stimulated B cells. B7-1 was not expressed on B cells under these conditions. The participation of B7-2 in the elicitation of the proliferative response of T cells was confirmed by the inclusion of anti-B7-2 antibody in cultures. The enhanced expression of either HSA or ICAM-1 was shown not to play a major role in the increased B cell antigen presentation capacity. The major T cell population responding to this activated B cell antigen presentation was shown to be CD44low naive CD4+ T cells, whereas CD45RBlow memory CD4+ T cells responded only weakly. The difference in proliferative responses between naive and memory CD4+ T cells was explained by the different efficiency in IL-2 production of these cell populations in response to antigen presentation by B cells activated by anti-mu plus IFN-gamma. These results suggest that IFN-gamma plays an important role in recruitment of naive T cells for an immune response.

Presentation of cartilage proteoglycan to a T cell hybridoma derived from a mouse with proteoglycan-induced arthritis

Immunization of BALB/c mice with human fetal cartilage proteoglycan (PG) produces progressive polyarthritis, and T cells play key roles in the development of the disease. To gain an understanding of how PG is presented to autoreactive T cells by synovial antigen-presenting cells (APC), we examined the abilities of various syngeneic APC in presenting PG to a specific T cell hybridoma 5/4E8, derived from a mouse with PG-induced arthritis. A20 B lymphoma cells and spleen cells were strong presenters of PG, but synoviocytes and P388D1 macrophages could only present PG effectively after stimulation with interferon-gamma (IFN-gamma). The IFN-gamma exerted its effect by up-regulating both MHC class II and intercellular adhesion molecule-1 (ICAM-1) expression by these cells as neutralizing antibodies to Ia, LFA-1 and ICAM-1 inhibited presentation. Our studies also showed that synoviocytes and spleen cells took up and processed PG more rapidly than the cell lines. Cysteine and serine protease-dependent antigen presentation of PG was blocked at 4 degrees C, 18 degrees C and by chloroquine treatment, indicating that presentation required active uptake and processing in an acidic compartment, probably in lysosomes. Also, keratan sulphate-depleted and cyanogen bromide (CNBr) and 2-nitro-5-thiocyanobenzoic acid (NTCB)-cleaved PG elicited stronger T cell responses, as they were more easily processed than the native molecule. Furthermore, CNBr-generated peptides were presented by fixed APC, indicating that core protein fragments of cartilage PG can be presented directly by APC in context with MHC class II molecules.

Interferon-gamma but not granulocyte/macrophage colony-stimulating factor augments proteoglycan presentation by synovial cells and chondrocytes to an autopathogenic T cell hybridoma

Immunization of BALB/c mice with human cartilage proteoglycan (aggrecan) produces a progressive polyarthritis, similar in many aspects to human rheumatoid arthritis, and autoreactive T cells are necessary for initiation of the disease. To study the immunopathological mechanisms operating in the synovium of arthritic mice, we isolated a proteoglycan (PG)-specific arthritogenic T-cell hybridoma, 5/4E8, and examined the presentation of PG to this T-cell hybridoma by mouse synovial cells and chondrocytes. Both cell types expressed very low levels of major histocompatibility complex (MHC) class II following isolation and culture and were unable to present PG to the hybridoma. However, following stimulation with interferon-gamma (IFN-gamma), both synovial cells and chondrocytes showed a marked increase in MHC class II expression and consequently were able to present PG very effectively. The PG-specific responses of the hybridoma were abrogated by an anti-Ia monoclonal antibody. Granulocyte-macrophage colony-stimulating factor (GM-CSF), one of the most abundant cytokines in the rheumatoid synovium, had no effect on the antigen-presenting capacity of synovial cells and chondrocytes, either on its own or together with IFN gamma.

Spleen cells from antigen-minimized mice are superior to spleen cells from germ-free and conventional mice in the stimulation of primary in vitro proliferative responses to nominal antigens

T lymphocytes from mice reared under conditions of differential exposure to food, environmental and microbial antigens were compared for phenotypic shifts that may be associated with prior exposure to antigens as well as functional variations in the ability to respond to antigens de novo. While the intra-epithelial CD8 T cell compartment was found to differ significantly in the type of T cell receptor predominantly expressed, CD4 T cells from various lymphoid organs of conventionally reared specific pathogen-free (CL-SPF) mice showed only subtle phenotypic differences from cells obtained from antigen-minimized germ-free (AF) and germ-free (GF) mice. Cells derived from mice exposed to a reduced antigen load exhibited primary in vitro proliferative responses to antigens such as dinitrophenyl-keyhole limpet hemocyanin which were significantly enhanced when compared with similar responses of cells from conventional mice. In cell mixing experiments, differences in the reactivity of T cells from the spleens of AF, GF and CL-SPF mice were dependent on the source of the spleen cells employed as antigen-presenting cells (APC). Experiments in which the T cell population was held constant revealed that, as APC, spleen cells from AF mice were most often superior to spleen cells from GF mice which were in turn considerably better than a similar population from SPF mice. We conclude that the enhanced primary reactivity of spleen cells from AF mice to nominal antigen in vitro is likely to be the result of a difference in the function and/or regulatory activities of the cell population employed as APC in this investigation.

Twenty years into the saga of MHC-restriction

Twenty years ago, the terms 'altered self' and 'H-2 restriction', later modified to 'MHC-restriction', were coined to describe the finding by Peter Doherty and Rolf Zinkernagel that murine cytotoxic T cells (CTL) would lyse virus-infected target cells only if effector and target cells were H-2 compatible. This short review recalls those heady days and briefly recounts some of the later findings in three aspects of particular interest raised by the original finding: the nature of the T cell receptor, the composition and structure of the ligand on the target cell recognized by the TCR and the importance of CTL in the control and clearance of infections in general.

Immunodeficiency due to a faulty interaction between T cells and B cells

The identification of the ligand for CD40, gp39, which is expressed on the membrane of activated CD4+ T-helper cells, has sparked intense investigation into the roles of this molecule in physiological B-cell activation. Recently, it has become clear that some human immunodeficiencies, such as X-linked hyper IgM syndrome and common variable immunodeficiency are linked to mutations in the gp39 gene or are a result of defective expression of gp39, leading to suboptimal, or a lack of, B-cell activation by T-helper cells.

The invariant chain induces compact forms of class II molecules localized in late endosomal compartments

The invariant chain (Ii) binds to newly synthesized major histocompatibility complex (MHC) class II molecules and is targeted to an acidic compartment where it is degraded. To evaluate its role on the conformation and the subcellular distribution of murine MHC class II molecules we have established stable L cell transfectants expressing class II IAk heterodimers alone or in conjunction with p31 and p41 Ii chains. In these cells, class II molecules were present under three forms: alpha beta heterodimers bearing high mannose carbohydrate moieties, and fully glycosylated alpha beta heterodimers that are sensitive or resistant to sodium dodecyl sulfate dissociation at 20 degrees C. The latter class II molecules called compact heterodimers, were here highly induced in Ii-positive cells. Using in situ iodination of endosomal compartments, class II heterodimers were detected in late endosomal compartments essentially as compact forms in Ii-positive cells, and as non-compact forms in Ii-negative cells. Using confocal microscopy, IAk molecules were located in compartments distinct from early endosomes labeled with transferrin, but partially coincident with vesicles containing fluid-phase markers, and highly coincident with compartments containing large amounts of cathepsins B, D, H, and L in Ii-positive and Ii-negative cells. At the ultrastructural level, class II molecules were mostly present in multivesicular bodies, even without Ii expression. But Ii chains were needed to induce an efficient presentation of the hen egg lysozyme antigen and were sufficient to promote a major conformational change of the late endosomal, and/or lysosomal resident, class II molecules. Ii molecules are presumably playing a chaperoning function favoring the association of peptides with class II molecules in endosomal compartments.

Mechanism of action of hydroxychloroquine as an antirheumatic drug

The antimalarial agents chloroquine and hydroxychloroquine have been used widely for the treatment of rheumatoid arthritis and systemic lupus erythematosus. These compounds lead to improvement of clinical and laboratory parameters, but their slow onset of action distinguishes them from glucocorticoids and nonsteroidal antiinflammatory agents. Chloroquine and hydroxychloroquine increase pH within intracellular vacuoles and alter processes such as protein degradation by acidic hydrolases in the lysosome, assembly of macromolecules in the endosomes, and posttranslation modification of proteins in the Golgi apparatus. It is proposed that the antirheumatic properties of these compounds results from their interference with "antigen processing" in macrophages and other antigen-presenting cells. Acidic cytoplasmic compartments are required for the antigenic protein to be digested and for the peptides to assemble with the alpha and beta chains of MHC class II proteins. As a result, antimalarials diminish the formation of peptide-MHC protein complexes required to stimulate CD4+ T cells and result in down-regulation of the immune response against autoantigenic peptides. Because this mechanism differs from other antirheumatic drugs, antimalarials are well suited to complement these other compounds in combination drug therapy.

Hydroxychloroquine treatment for primary Sjögren's syndrome: a two year double blind crossover trial

OBJECTIVES

In 1985 and 1988 a positive effect of treatment of primary Sjögren's syndrome with hydroxychloroquine was reported in two small open studies. To investigate further the clinical and laboratory effects of hydroxychloroquine in primary Sjögren's syndrome a two year study was performed.

METHODS

The design of the study included a prospective, placebo controlled, two year double blind crossover trial in 19 patients.

RESULTS

A significant decrease in IgG and IgM and a tendency for a decrease in the erythrocyte sedimentation rate (ESR) during treatment with hydroxychloroquine compared with treatment with placebo were found. No beneficial clinical effect of the use of hydroxychloroquine as expressed in preference for treatment with hydroxychloroquine or placebo with regard to symptoms and signs of primary Sjögren's syndrome could be shown, however, nor any relevant change in tear gland activity and sequelae of peripheral tear function deficiency, nor salivary gland scintigraphy.

CONCLUSIONS

The use of hydroxychloroquine at a dose of 400 mg daily taken over a 12 month period does not have a worthwhile clinical benefit in patients with primary Sjögren's syndrome despite an improvement of hyperglobulinaemia and slight changes in the ESR and IgM.

A rational design of synthetic peptide vaccine with a built-in adjuvant. A modular approach for unambiguity

We describe a peptide vaccine model containing a built-in adjuvant. This model used a multiple antigen peptide system (MAPS) to amplify peptide antigens and a lipoamino acid, tripalmitoyl glyceryl cysteine (P3C), as a built-in adjuvant. An 18-residue peptide antigen (B2) derived from the third variable domain (amino acid 312-329) of the glycoprotein gp120 of type I human immunodeficiency virus (HIV-1) was used in this model. This peptide antigen is a suitable target since it consists of neutralizing, T-helper, and T-cytotoxic epitopes. The peptide antigen in a tetravalent MAPS format (B2M-P3C) with a lipophilic attachment was synthesized by two routes for comparison: a direct stepwise approach and an indirect modular approach. In the stepwise approach, each residue was sequentially added to the peptide resin to give B2M-P3C and the P3C was incorporated to the side chain of a carboxyl terminal lysine as Fmoc-Lys(P3C). In the modular approach, a module containing a chloroacetylated core matrix of MAPS (M-P3C) with a carboxyl tetrapeptide bearing Lys(P3C) and a second module containing the peptide antigen B2 with a cysteine at its terminus were synthesized and purified separately, and then coupled to each other to form B2M-P3C. In the modular approach, the molecular ion of B2M-P3C was unambiguously identified by ion-spray mass spectrometry. B2M-P3C, administered in liposomes without any adjuvant such as Freund's complete adjuvant, was used to immunize mice and found to induce gp120-specific antibodies in vitro, and prime cytotoxic T lymphocytes in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Papillon-Lefevre syndrome. Characterization of peripheral blood and gingival lymphocytes with monoclonal antibodies

A 14-year-old boy with typical features of Papillon-Lefevre syndrome (PLS) is presented. The purpose of this report was to study the immunopheno-typic features of the peripheral blood and gingival tissue lymphocytes with monoclonal antibodies in the patient. Peripheral blood T-cells, helper-T cells, suppressor-T cells, HLA-DR+ cells and IL-2R+ cells were determined using appropriate monoclonal antibodies and indirect immunofluorescence methods. B-cells were identified using the direct immunofluorescence technique. The gingival tissue was processed for both histopathological and immunohistological examinations. Gingival tissue lymphocytes were identified using monoclonal and polyclonal antibodies with the immunoperoxidase technique. Although we have not detected any significant alterations in the peripheral blood B-cell and T-cell populations, NK cells were significantly increased. HLA-DR+ cells and IL-2R+ cells were within normal limits. Histopathology of the diseased tissue revealed predominance of plasma cells in the lamina propria. The majority of the plasma cells were bearing IgG isotype. Most of the CD3+ T-cells were located beneath the pocket epithelium with an almost equal distribution of CD4+ and CD8+ T-lymphocytes, in situ. These findings indicate that PLS is a IgG+ plasma cell dominated lesion with the participation of T-lymphocytes, having similar distributions of both subsets. While the etiopathogenesis of the syndrome still has to be elucidated, these immunohistological findings could be used for further studies in this intriguing entity.

HLA-DR peptide-induced alloreactive T cell lines reveal an HLA-DR sequence that can be both "dominant" and "cryptic": evidence for allele-specific processing

Previously, we reported on a T cell line, ThoU6, which we obtained through stimulation of DPw3+ cells with a synthetic "DR3 peptide" with a sequence identical to the third hypervariable region of the DRB1*0301 chain. This T cell line recognizes both the synthetic peptide presented by DPw3 as well as DR3+ DPw3+ stimulator cells. This implies that the synthetic DR3 peptide has a natural counterpart in DR3-positive cells. Here we describe the recognition pattern of another T cell line that was sensitized with the same synthetic DR3 peptide. This T cell line, BieU6, shows both HLA-DRw13/Dw18 (self)-restricted recognition of the synthetic DR3 peptide and allorecognition towards DR13/Dw19, a molecule which is highly homologous to Dw18, in the absence of synthetic peptide. These results suggest that the epitope formed by the Dw18 molecule plus the synthetic DR3 peptide and recognized by T cell line BieU6 mimics the Dw19 molecule. The potential role for a Dw19-specific peptide is discussed. The inability of T cell line BieU6 to recognize Dw18+ DR3+ cells indicates that, in this case, the synthetic DR3 peptide is "cryptic", i.e. does not have a natural counterpart that is effectively presented to T cells. Mapping of the shortest peptides recognized by T cell lines ThoU6 and BieU6 indicate that these sequences are fully overlapping. We, therefore, suggest that the antigen-presenting molecules, HLA-DPw3 and HLA-Dw18, differ in their accessibility for self peptides derived from the third hypervariable region of DR molecules. These observations may be explained by allele-specific processing.

Class II (I-Ad) restricted T-cell recognition of the V3 loop region of HIV-1 gp120

A CD4+ and gp120-specific T-cell line, and subclone, were established from BALB/c mice following immunization with recombinant gp120, using an adjuvant formulation (alum) acceptable for use in the human. The recognition specificity was determined against a panel of synthetic peptides corresponding to the primary sequence of the HXB2 strain of human immunodeficiency virus (HIV). An epitope was identified, corresponding to amino acid residues 322-341, and a further series of truncated peptides established the minimum determinant to be 327-341. Possible reasons for the immunodominance of the V3 loop, and adjacent regions, for both antibody and T-cell recognition are discussed.

HLA-DR expression in macaque neuroendothelial cells in vitro and during SIV encephalitis

HLA-DR expression in neuroendothelial cells (NEC) was studied during the course of SIV encephalitis in rhesus monkeys. HLA-DR determinants were detected on NEC in monkeys with SIV encephalitis, but not in control animals. In situ hybridization with an SIV probe indicated that HLA-DR expression was not a consequence of SIV replication within NEC. Cultured rhesus NEC stimulated with gamma interferon expressed HLA-DR to a higher degree than cultured brain fibroblasts or astrocytes. These data support the contention that NEC participate in retrovirus-induced inflammation and autoimmunity within the central nervous system.

Macrophages and migratory cells in endometrium relevant to implantation

The implantation of an appropriately developed embryo into a suitably conditioned uterine lining depends on the synchronous maturation of the preimplantation embryo and uterine lining. The pre- and postimplantation embryo also requires protection from immunocompetent maternal immune effectors. Preimplantation embryo development is affected by genotype, intercellular communication and autocrine growth factors (polyamines, TGF-alpha, TGF-beta 1, PAF). Factors of maternal origin may also enhance embryo development (EGF, TGF-alpha, TGF-beta 1, IGF, polyamines). The preimplantation embryo signals its presence to the mother by release of factor(s) such as IFN-alpha-II and a PAF-like factor. PAF may induce EPF in the mother and enhances vascular permeability at the implantation site. Uterine or peritoneal leukocytosis may inhibit development via toxic effects of lymphokines/monokines (IL-2, IL-1?, IFN-gamma, TNF-alpha). Immunoprotection of the preimplantation embryo is conferred by embryo derived maternal factors (EPF, T-cell suppressor factors). The uterus is receptive during a limited period of time (implantation window) and the substrate adhesion molecules produced by uterine and embryonic trophectoderm cells are crucial for the initial stages of implantation. At implantation, trophoblast expression of MHC and non-MHC antigens is shut off and both immunocompetent maternal cells (macrophages, dendritic cells, granulocytes, IELs, immunocytes) and lymphatics become sparse at implantation sites. Peri-implantation cytokines of maternal origin, such as CSF-1, GM-CSF and IGF-1 binding protein, are probably important for trophoblast growth and development. Immuno-protection of the embryo at this stage may be mediated by embryo derived factors that inactivate macrophages and by a population of large, hormone dependent Lyt 2+ (CD8+) suppressor cells. It is possible that these CD8+ cells respond to progesterone and secrete molecules that inactivate natural effector (NK-type) cells against trophoblast. Prostaglandins (PGE2) may play a brief role in immunosuppression at the time of implantation but its role is probably more important with respect to the decidual response. Defects in the pre- and peri-implantation stages of pregnancy may lead to delayed failure in the form of clinical miscarriage.

Structural aspects of a protein epitope and their role in the major histocompatibility complex control of T cell responsiveness

We have previously shown that immunization of C57BL/10 (H-2b) mice with the tobacco mosaic virus protein (TMVP) or with its tryptic peptide number 8, representing residues 93-112 of TMVP, induces T cells which proliferate in vitro in response to TMVP and peptide 8. In contrast, immunization of congenic B10.BR (H-2k) mice with either TMVP or with peptide 8 induces T cells which respond in vitro to the homologous but not the heterologous antigen. The capacity to exhibit cross-reactivity between TMVP and peptide 8 on the T cell level has been shown to be under major histocompatibility complex (MHC)-linked genetic control. The lack of cross-reactivity has been attributed to the inability of the H-2k APC to present the appropriate epitope to T cells. In the present paper, we report results of a comparative analysis of the role of structural aspects of the epitope on the proliferative T cell responses from TMVP and peptide 8-immune C57BL/10 (H-2b) and B10.BR (H-2k) mice. Utilizing a panel of synthetic peptides representing portions of peptide 8 and a panel of peptide-protein conjugates, we have determined that peptide 8-immune T cells of the H-2k strain appear to recognize a single epitope within peptide 8, located at its N-terminus. In contrast, in the H-2b strain, both TMVP and peptide 8-immune T cells appear to recognize two overlapping epitopes within peptide 8; one located in the middle region and the other toward the N-terminus. Experiments with H-2b T cells revealed that random amino acids added to the carboxyl or amino-terminus of nonstimulatory peptides can confer activity to these peptides, demonstrating limited specificity of interaction between antigen and Iab. Results of experiments dealing with fixation of antigen-presenting cells suggest that TMVP requires processing in order to be recognized by peptide 8-immune H-2b proliferative T cells whereas peptide 8 does not. Taken together the results suggest that the T cell responsiveness to TMVP and peptide 8 exhibited by these two congenic strains H-2b and H-2k is not only controlled by the strains MHC but is also influenced by antigen processing. Antigen processing may eliminate a potential epitope for the primary induction and the secondary stimulation of B10.BR T cells.

Identifying antigenic T-cell sites

Computer algorithms that have been used successfully on protein sequences for the prediction of antigenic T-cell sites have been collected into a single computer software package called TSites.

Binding of peripheral blood and thyroidal T lymphocytes to thyroid cell monolayers: possible role of "homing-like" receptors in the pathogenesis of thyroid autoimmunity

The specific binding of blood lymphocyte populations to non-antigenic receptors on high endothelial cells in peripheral lymphoid organs is well established. Such "homing" receptors in target tissues may also play a role in the early phase of organ specific autoimmunity. In this study binding of peripheral blood and thyroid-derived T cells to human thyroid (THY) cells was examined. Binding was measured as the percentage 51Cr-labelled T cells bound to THY monolayers. Interferon-gamma (IFN-gamma) enhanced the binding of peripheral blood T cells (PBL-T) from patients with Graves' disease (GD) and normals, but not from patients with Hashimoto's thyroiditis (HT), to allogeneic THY monolayers. The binding of T cells from patients with HT to untreated allogeneic THY monolayers was significantly greater than that for T cells from patients with GD or normals. TSH inhibited the IFN-gamma enhancement of binding of PBL-T from 4 normals and one HT patient to both allogeneic (n = 5) and autologous (n = 4) THY monolayers. Intra-thyroid T cells (ITL-T) bound to autologous THY monolayers significantly more than PBL-T from the same patient, while ITL from patients with HT or Graves' disease bound more than their PBL-T to both allogeneic and autologous THY monolayers. ITL-T, but not PBL-T, bound significantly more to autologous THY than to autologous thyroid-derived fibroblast monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of monocytes in anti-CD3-induced T-cell DNA synthesis: effect of chloroquine and monensin on anti-CD3-induced human T-cell activation

Anti-CD3 monoclonal antibody (MoAb) induces proliferation of freshly isolated peripheral blood T cells only in the presence of monocytes/macrophages and requires binding of the Fc portion of antibody to monocytes/macrophages. In this investigation, we examined whether monocytes process anti-CD3 similar to any soluble antigen and present to T cells in context with HLA-DR to induce maximal DNA synthesis. Adherent monocytes were pulsed with anti-CD3 MoAb in the presence or absence of the lysozomotropic agents chloroquine and monensin, which are known to inhibit processing of soluble antigens, washed extensively, and then incubated with autologous T cells in the absence of soluble anti-CD3, and 3H-thymidine incorporation and CD25 expression were measured. Both monensin and chloroquine inhibited anti-CD3-pulsed monocyte-induced T-cell DNA synthesis and CD25 expression in a dose-dependent manner. This inhibitory effect was not due to any loss in cell viability or the effect on the expression of HLA-DR on monocytes. Paraformaldehyde-fixed monocytes pulsed with anti-CD3 MoAb induced significantly less DNA synthesis, HLA-DR expression, and CD25 antigen expression on autologous T cells as compared to responses induced by unfixed anti-CD3-pulsed monocytes. The treatment of anti-CD3-pulsed monocytes with framework-specific anti-HLA-DR MoAb inhibited their capacity to induce T-cell DNA synthesis. These data suggest that monocytes, in addition to serving as the matrix for cross-linking, also process anti-CD3 MoAb and present to the T cells in the context of HLA-DR antigens to induce optimal DNA synthesis.

Immune responsiveness of neonatal chicks and immunocyte precursors from unprimed juvenile chicken donors

The immune responsiveness of immunocyte precursors, obtained from peripheral blood of 4- to 6-wk-old unprimed chickens and assayed with the cell transfer model, was compared with that of neonatal chicks. Little if any splenic plaque-forming cell (PFC) production was observed in the spleens of embryonic cell transfer hosts following a single antigen exposure to weak or moderate dosages of mammalian erythrocytes. However, modest to high PFC formation occurred consistently in the hosts following a second exposure to the same antigen when given 3 days later. Although a single immunization failed to elicit PFC formation in embryo hosts, a single injection of a wide range of antigen dosages into 8-day-old chicks elicited PFC production consistently. When the double immunization protocol was used with 2- to 9-day-old neonatal chicks, the level of immune responses were indistinguishable from those elicited with a single antigen injection. The difference in the immune kinetics observed in embryo hosts may be related to the embryonic microenvironment, which is permissive, but may not be as immunosupportive as that of neonates.

Dissociation between allogeneic T cell stimulation and interleukin-1 or tumor necrosis factor production by human lung dendritic cells

A small portion of human lung mononuclear cells are very potent stimulators of allogeneic resting T cells. Although several-fold more effective than phagocytic alveolar macrophages (AM) and blood monocytes (Mo), they do not produce more of the lymphocyte co-stimulators interleukin-1-alpha (IL-1 alpha), interleukin-1-beta (IL-1 beta), or tumor necrosis factor-alpha (TNF-alpha) than did Mo. Blocking antibodies against IL-1 alpha, IL-1 beta, TNF-alpha, and IL-6 did not reduce T cell proliferation. These potent antigen-presenting cells (APC) are loosely adherent and do not have phagocytic inclusions. Most of them have the marker RFD1 of dendritic cells (DC) rarely present on Mo or AM and have a strong tendency to form clusters with T cells like murine DC. Thus, we demonstrate an example in the human system of a dissociation between T cell activation and IL-1 or TNF-alpha production by DC or Mo, implying a major role for other "co-stimulating signals" by lung APC with dendritic features. The presence of different APC with various co-stimulating signals may be of importance for T cell subsets modulation.

T lymphocyte aggregation with immobilized anti-TCR-antibodies is dependent upon energy and microfilament assembly

An assay has been developed to quantitate the binding of beads coated with anti-T cell receptor (TCR) monoclonal antibodies (MoAb) to T lymphocytes. The Ab used were a hamster MoAb, 145.2C11 (2C11), directed against the epsilon chain of the CD3 complex of the murine TCR, and a murine MoAb, F23.1, directed against the V beta 8-encoded determinant of the alpha/beta heterodimer of the TCR. Ab were adsorbed onto polystyrene beads and the beads labeled with [125I]bovine serum albumin [( 125I]BSA). The labeled, Ab-coated beads were mixed at 4 degrees C with murine, cloned T-helper (Th) cells and contact between beads and cells was promoted by centrifugation. The mixtures were incubated at 37 degrees C for 10-20 min, and unbound beads were separated from cell-bound beads by Percoll gradient centrifugation. Beads coated with anti-TCR Ab formed stable conjugates with Th cells; an average of 6-10 2C11 Ab-coated beads/cell, or 10-15 F23.1 Ab-coated beads/cell was measured under optimal conditions. Beads coated with control Ab (hamster or mouse IgG) did not appreciably bind to the cells. Conjugation with 2C11 Ab-coated beads could be prevented by coating the cells with soluble 2C11 Ab, but not with soluble F23.1 Ab. Blocking the CD3 epsilon chain with soluble 2C11 Ab also reduced conjugate formation with F23.1 Ab-coated beads, suggesting a steric hindrance phenomenon. The extent of conjugation depended on the density of immobilized Ab. Maximum conjugation was observed when 100 micrograms of 2C11 Ab was used to coat 10(6) beads; higher Ab amounts did not further increase binding. Increasing the bead to cell ratio in the mixture increased binding, reaching optimal binding at 300:1, irrespectively of the amount of Ab adsorbed onto the beads. Stable binding of anti-TCR Ab-coated beads to T cells was temperature and energy dependent. It was prevented when glucose was removed from the medium and the glycolysis inhibitor, 2-deoxy-D-glucose was added, or when cells were treated with sodium azide. Conjugate formation was prevented by pretreatment of the cells with cytochalasins, indicating that microfilament assembly was essential. Microtubules were not involved, as vinca alkaloids were without effect. This novel assay system provides a simple means of studying aspects of TCR function including its physical and metabolic regulation.

Immunosuppression by pulmonary surfactant: mechanisms of action

Pulmonary surfactant has been shown by this group to suppress peripheral blood lymphocyte responses to mitogens and alloantigens in a dose dependent manner, though the mechanism of action of the suppressive effect is not clearly understood. To try to clarify this, attempts were made to reverse the effects of preincubation with surfactant, obtained by bronchoalveolar lavage from pigs, on lymphocytes and accessory monocytes obtained from the blood of normal volunteers, by washing and incubating the cells in medium alone for various periods up to 24 hours. Immunosuppression, measured as the reduction in thymidine incorporation in response to the mitogen phytohaemagglutinin, could not be reversed by these methods. The addition of indomethacin (up to 100 micrograms/ml for 72 hours) also had no effect, indicating that the immunosuppression was not related to synthesis of prostaglandins. Incubation with surfactant for as little as two hours before addition of mitogen suppressed in vitro lymphoproliferative responses by half, but surfactant added two hours after mitogen had no observed effect. Preincubation of purified lymphocytes in surfactant, before they were cultured with accessory monocytes and mitogen, caused significant suppression of response, but preincubation of purified monocytes had no suppressive effect. There was no change in the intensity of HLA-DR expression on monocytes. These results support the hypothesis that surfactant exerts its effects on the resting uncommitted lymphocyte rather than on antigen presenting monocytes.

Expression of MHC class I and class II antigens in colonic carcinomas

Malignant and non-malignant ('normal') colonic tissues from patients with colonic carcinoma were examined for the expression of MHC class I and class II antigens by immunoenzymatic staining using monoclonal antibodies. The amount of class I antigen as detected by 2 monoclonal antibodies, FMC 16 or W6/32 was clearly diminished in 11 of 14 tumours when compared to the amount present on 'normal' colonic tissue from the same individual. The loss of class I antigen did not correlate with tumour stage or differentiation. The reactivities of FMC 16 and W6/32 with these tissues were not identical, which indicates that the 2 monoclonal antibodies may recognize different epitopes on the HLA class I molecule. Class II antigens were absent from 'normal' colonic epithelium but were present on 20 of 28 tumours, with DR being detected more often than DP, and DQ found only on 4 of 28 tumours. When present, staining for class II antigens was heterogeneous within the tumour, in that all tumour cells did not stain equally. DR and DP antigens were found more often on moderately or poorly differentiated adenocarcinomas and on stage B, C and D tumours in that order of frequency. Thus tumours with a better prognosis were less likely to express DR and DP. The expression of DQ was unrelated to staging or differentiation.

Thymosins alpha 1 and beta 4 potentiate the antigen-presenting capacity of macrophages

The immunomodulatory effects of thymosins on the Ag-presenting capacity of macrophages were investigated. Using an in vitro antigen (Ag)-specific macrophage-dependent T-cell proliferation system, we found that both thymosin alpha 1 (T alpha 1) and thymosin beta 4 (T beta 4) augment the Ag-presenting capacity of macrophages. Macrophage monolayers were pulsed with keyhole limpet hemocyanin (KLH) in the absence or presence of thymosins, washed and overlaid with spleen cells. Splenocytes were collected, mitomycin C-treated and injected into syngeneic mice. Draining lymph node cells were tested for Ag-specific response by measuring proliferation, interleukin 2 (IL-2) secretion and expression of IL-2 receptors (IL-2R) on their cell surface. We found that the presence of thymosins during the pulsing of macrophages with KLH led to significantly enhanced lymph node cell proliferation responses to KLH was correlated to increased IL-2 production and IL-2R expression. The concentrations of T alpha 1 and T beta 4 required for amplification were 10(-8) to 10(-10) M, well within the physiological range of activity of most peptide hormones. The observed enhancement of IL-2 secretion was not accompanied by interleukin 4 (IL-4) production. This study is the first to demonstrate that thymic hormones have the ability to increase the efficiency of antigen presentation by macrophages. The results suggest that an initial step in the regulation of the immune function by T alpha 1 and T beta 4 may involve activation of the macrophages at the time of antigen presentation.

Immunoglobulin-specific T-B cell interaction. I. Presentation of self immunoglobulin determinants by B lymphocytes

Immunoglobulin (Ig)-specific T-B cell interactions have been studied in the model of T cell recognition of the kappa chain Ig kappa-1b allotype in Ig kappa-1-congeneic rat strains. An efficient presentation of endogenous Ig allotypic determinants by irradiated spleen cells from (WAG.1b x August)F1 (RT-1u/c; Ig kappa-1b/1a) rats to Ig kappa-1b-specific lymph node T cells from Ig kappa-1-congeneic (WAG x August)F1 (RT-1u/c; Ig kappa-1a) rats was demonstrated. This presentation was found to be sensitive to high irradiation doses (greater than 1000 rad). By fractionation of Ig kappa-1b+ F1 spleen cells on Percoll density gradient we have shown that a radioresistant, low-density fraction, consisting mainly of macrophages (M phi) and dendritic cells, triggers only weak Ig kappa-1b-specific T cell response. The high level of response was observed against radiosensitive spleen cell fractions of intermediate and high density, suggesting that B cells were the main antigen-presenting cells (APC) of Ig kappa-1b determinants of endogenous Ig. This conclusion was confirmed in the experiments using purified B cells from Ig kappa-1b-bearing rats. Earlier we have shown that the responsiveness of August (RT-1c; Ig kappa-1a) and WAG (RT-1u; Ig kappa-1a) rats to Ig kappa-1b in vivo is controlled by the dominant allele of an RT-1-linked Ir gene. August and (August X WAG)F1 rats were found to be responders to Ig kappa-1b while WAG rats were nonresponders. The same pattern of Ir gene-controlled reactivity was demonstrated using an Ig kappa-1b-specific T cell proliferation assay. Ig kappa-1b-specific F1 T cell response was only observed when Ig kappa-1b+ B cells or IgG (Ig kappa-1b)-pulsed M phi-bearing responder major histocompatibility complex (MHC) haplotype were used as the APC. Anti-RT-1 monoclonal antibody inhibition studies suggested that the RT-1Bc molecule is the main restricting element of T cell recognition of Ig kappa-1b+ B cell as well as exogenous IgG (Ig kappa-1b). We have demonstrated allelic exclusion of Ig kappa-1b presenting function by negatively and positively selecting for Ig kappa-1b+ and Ig kappa-1a+ B cells from heterozygous F1(Ig kappa-1b/1a) rats. This clearly indicate that the B cells presented exclusively Ig kappa-1b allotypic determinants of their own Ig.(ABSTRACT TRUNCATED AT 400 WORDS)

PGE2-induced cyclic AMP accumulation in human CD4+ T cells is strongly enhanced during the CD2-mediated activatory process

The effect of a mitogenic combination of two different anti-CD2 monoclonal antibodies on the PGE2-stimulated and basal cAMP production in human CD4+ T cell clones was investigated. The anti-CD2 stimulation strongly potentiates the PGE2-induced cAMP production while both PMA and A23187 produced a less potent effect. On the opposite the anti-CD2 treatment is without any effect on the basal cAMP level contrasting with a marked increase of intracellular cAMP concentrations with A23187 or the combination of A23187 and PMA. These results suggest that activation of CD4+ human T cells via the CD2 molecule significantly influences the cAMP-related transduction pathway. Although PMA and A23187 also modulate the activity of this pathway, their effect in this model is more likely mediated through an amplification of basal cAMP production.

Class I MHC-restricted cytotoxic T cells efficiently recognize haemagglutinin that is defective in protein folding and cell surface expressions

Cytotoxic T-cell recognition of an engineered variant of the influenza viral haemagglutinin (HA), expressed in vaccinia virus, was investigated. We show that the insertion of a Foot-and-Mouth Disease virus (FMDV) immunogenic peptide into the HA results in major disruption of its higher order structure with intracellular rather than cell surface localization accompanying the loss of conformational epitopes detected by antibody. In contradistinction to antibody, recognition of the chimaeric molecule by HA-specific class I-restricted cytotoxic T-cells was unimpaired, demonstrating that class I-specific T-cells recognize, in majority, continuous epitopes rather than conformational epitopes in the HA.

A region of the influenza A/NT/60/68 PB2 protein containing an antigenic determinant recognized by murine H-2Dd restricted cytotoxic T lymphocytes

We have used a recombinant vaccinia virus to investigate the recognition of the PB2 protein of influenza A/NT/60/68 (H3N2) by murine polyclonal CTL populations. PB2 is recognized as a major cross-reactive target antigen. Recognition of PB2 is under strict genetic control, since BALB/c (H-2d) but not CBA (H-2k) mice are responders. We also demonstrate, by use of cell lines transfected with individual genes encoding class I molecules of the H-2d haplotype, that recognition of PB2 occurs in conjunction with the H-2Dd but not the H-2Kd or H-2Ld molecules. In contrast, recognition of the nucleoprotein of A/PR/8/34 by BALB/c-derived polyclonal CTL is restricted via the H-2Kd molecule. By using three recombinant vaccinia viruses expressing deleted forms of the PB2 protein we show that at least one epitope of the PB2 protein resides within the amino-terminal 256 amino acids. This approach offers an effective method to map the regions of large proteins containing epitopes recognized by CTL.

T cell hybridomas define the class II MHC-restricted response to vesicular stomatitis virus infection

T cell hybridomas with specificity for VSV (vesicular stomatitis virus)-infected cells were generated in an attempt to better define the la-restricted helper T cell response to VSV. The hybridomas were created by fusing BALB/c (H-2d) anti-VSV immune spleen cells to the murine thymoma BW 5147. These hybridomas produce IL-2 when stimulated with VSV-infected spleen cells. They were found to recognize viral antigens in association with I-Ad and, in addition, could also be stimulated by VSV-infected A20 cells (an Ia-positive B cell lymphoma of H-2d origin). The purified viral membrane glycoprotein, G protein, and Gs (secreted G protein that lacks the hydrophobic and intracytoplasmic domains) both stimulated IL-2 production when added to cultures of A20 and the hybridomas. These hybridomas therefore recognize a viral antigenic determinant on G protein. Since chemically-fixed antigen-presenting cells fail to stimulate the hybridomas after exogenous addition of purified G protein we can conclude that these T cell hybridomas recognize a processed form of the G protein. Stimulator cells created by expression in A20 of a transfected cDNA encoding G protein were also recognized. Recognition in this case was I-Ad-restricted, as anti-I-Ad monoclonal antibodies blocked stimulation, and an Ia-negative cell (P815) expressing a transfected G protein gene failed to stimulate the hybridomas. Even after paraformaldehyde fixation, G gene-transfected, Ia-positive cells could stimulate the hybridomas, suggesting that processing of this endogenously-synthesized antigen has occurred.

Treatment of primary Sjögren's syndrome with hydroxychloroquine

Sjögren's syndrome is an autoimmune disease characterized by lymphocytic infiltration of the salivary/lacrimal glands, autoantibody production, and polyclonal hyperglobulinemia. In view of the efficacy and relative safety of hydroxychloroquine in other autoimmune disorders, the potential benefit of hydroxychloroquine (200 mg per day for 12 months) in 10 patients with Sjögren's syndrome was evaluated. Changes in levels of total immunoglobulin, antibody against Sjögren's syndrome-associated antigen B, rheumatoid factor, and in vitro production of immunoglobulin in the serum were evaluated. For comparison, 10 patients matched according to age and sex, who did not receive hydroxychloroquine were studied. In the hydroxychloroquine-treated group, the following observations were made: (1) significantly decreased total immunoglobulin G (IgG) and IgA levels with little change in IgM levels; (2) significant decrease in IgA-rheumatoid factor with a smaller decrease in IgM-rheumatoid factor; (3) decreased IgG anti-Sjögren's syndrome-associated antigen B autoantibody; and (4) decreased erythrocyte sedimentation rate and increased hemoglobin level. Further, a specific idiotype present on their rheumatoid factor (defined by monoclonal antibody 17-109) was significantly decreased, with disappearance of detectable circulating paraprotein in two hydroxychloroquine-treated patients. Finally, rheumatoid factor production in vitro by lymphocytes from hydroxychloroquine-treated patients using a T cell-dependent mitogen was significantly decreased. These results suggest that hydroxychloroquine modulates lymphoproliferation in patients with Sjögren's syndrome and may prevent progression to extraglandular sites of neoplastic transformation.

Enhancement of antigen-presenting function of dendritic cells with culture supernatants of mouse peritoneal macrophages stimulated with certain particulate substances

The production from murine resident peritoneal macrophages (M phi) of a soluble factor, which was capable of enhancing the antigen-presenting (AP) function of dendritic cells (DC), was examined. The supernatants of peritoneal M phi (M phi sup) were prepared by culturing peritoneal M phi with particles, i.e., zymosan A, latex, and sheep red blood cells (SRBC), or antigen-antibody (Ag-Ab) complexes such as keyhole limpet hemocyanin (KLH)-anti-KLH, ovalbumin (OVA)-anti-OVA, and SRBC-anti-SRBC complexes. When exposed to M phi sup during antigen pulsing DC induced a marked antigen-specific T cell proliferation, relative to DC treated with the supernatants from M phi cultured without stimuli (control sup). On the other hand, M phi sup-treated splenic M phi stimulated antigen-specific T cell activation to almost the same extent as did splenic M phi treated with control sup. These results indicated that peritoneal M phi elaborated a soluble factor which preferentially enhanced the AP capacity of DC when stimulated with particles or Ag-Ab complexes. Analytical gel filtration of M phi sup revealed that the factor had an apparent molecular weight of 27,000 daltons which was distinct from interleukin 1.

Alloantigen presenting capacity of human decidual tissue

The capacity of first trimester human decidua-derived cells to serve as accessory cells for the presentation of alloantigens to unprimed T lymphocytes was assessed using a mixed lymphocyte culture (MLC) between accessory cell-depleted responder and stimulator peripheral blood lymphocytes (d PBL). In all of the seven experiments performed decidua-derived cells achieved significant reconstitution of the lymphoproliferative response between autologous responder and stimulator dPBL. Reconstitution indices (RIs) ranged between 3.1 and 22.2 and were significant in all cases. In six out of the seven experiments the level of lymphoproliferation exceeded that between untreated responder PBLs co-cultured with stimulator d PBL. Substitution of recombinant interleukin 1 (rIL-1) alpha or beta for the decidua-derived cells resulted in significantly lower RIs than those achieved by the decidua-derived cells. These findings suggest that decidua-derived cells can serve as antigen presenting cells for the presentation of membrane-bound alloantigens in a primary lymphoproliferative response. This may have implications for maternal recognition of fetal antigens during first pregnancy.

Stromal cell lines which support lymphocyte growth: characterization, sensitivity to radiation and responsiveness to growth factors

Stromal cells which grow as an adherent layer of Whitlock-Witte cultures are thought to be an essential component of the lymphohemopoietic microenvironment. Stromal cell lines from bone marrow (BM) and spleen have been obtained by treatment of cultures with 5-fluorouracil and selected for their lymphocyte support capacity by measuring the clonal growth of stromal cell-dependent lymphocyte lines in methyl cellulose. Established stromal cell lines differed significantly from stromal cells in primary Whitlock-Witte cultures with respect to expression of certain hemopoietic cell surface markers. For example, the Thy-1 and Mac-3 antigens were expressed by stromal cell lines obtained from BM and spleen, but not by stromal cells in primary cultures. Features common to all stromal cells include synthesis of actins, the neural adhesion molecule N-CAM, and a variety of collagens. Two types of common leukocyte antigens were not significantly expressed. The proliferation and total protein synthetic capacity of lymphocyte-supportive stromal cell lines was sensitive to ionizing radiation. After exposure of the cells to 200 rads, the incorporation of either [3H]thymidine or [3H]Leucine was reduced to less than 50% of control values, but the growth of lymphocytes was augmented in the presence of an irradiated stromal cell layer. The proliferation of stromal cell lines was also affected by exposure to a variety of growth factors. Addition of epidermal growth factor or endothelial cell growth factor augmented BM or spleen-derived stromal cell proliferation, while interferon-gamma had the opposite effect. In general, but not exclusively, lymphocyte growth was inhibited by factors which augmented the proliferation of stromal cells. Novel methods are described for isolating stromal cells and determining their capacity to support lymphocyte growth in vitro. Evidence is presented that this ability is not restricted to BM-derived stromal cells. The function of stromal cells was not dependent on their ability to proliferate, and this may be modulated by immunoregulatory and other growth factors.

Effect of diisopropylfluorophosphate on the antibody response

The impact of the in-vivo administration of diisopropylfluorophosphate (DFP) on the antibody response in mice was examined. The antigen-specific plaque-forming cell (PFC) response of mice injected with DFP (4 mg/kg) at the time of immunization with a macrophage-dependent T-cell antigen, trinitrophenylated keyhole limpet hemocyanin (TNP-KLH) or sheep red blood cells (SRBC), was significantly depressed. In contrast, the injection of a similar dose of DFP had no effect on the PFC response of mice immunized with a macrophage-independent B-cell antigen, lipopolysaccharide (LPS). This differential effect suggests a possible detrimental effect of DFP on cells involved in antigen processing and/or presentation which are required for the antibody response to SRBC and TNP-KLH. These results, however, do not exclude T cells as a possible target and the cellular targets of DFP action remain to be established. The DFP-mediated depression of the PFC response to SRBC was still evident when DFP was given as early as 1 day before, but not 1 day after, the injection of antigen, suggesting that DFP may well affect an early event of the antibody response. For the secondary TNP-specific IgM PFC response, a significant depression was observed only when DFP was administered at the time of antigen challenge. The injection of DFP at the time of antigen priming, however, was effective in depressing the IgG, but not the IgM, PFC response. Therefore, DFP may also interfere with the generation of antigen-specific memory cells for the secondary IgG response.