Cell-mediated Immune Mechanisms Research Articles

In situ immunophenotype of macrophages and lymphocytes in granuloma formation of tuberculous lymphadenitis in HIV-infected and immunocompetent patients

The phenotype of inflammatory cells in lymph nodes from 16 patients with culture-proven tuberculous lymphadenitis were examined by histological and immunohistochemical techniques. Eight patients were suffering from a symptomatic HIV1 infection and 8 patients were immunocompetent individuals without positive HIV1 serology. In addition, the lymph nodes of 2 AIDS patients with Mycobacterium avium-intracellulare infection were examined using the same techniques. Characteristic granulomas with or without caseation were observed in the 8 immunocompetent and the 4 HIV1-infected patients with less marked lymphopenia of CD4 + peripheral blood lymphocytes (PBL). In lymph nodes from the other HIV1-infected patients with more severe depression of CD4 + PBL, no epithelloid cell formation was present; instead, foamy macrophages were found. The phenotype of the macrophages underwent progressive changes in parallel with the decreasing numbers of CD4 + PBL. Foamy macrophages in M. avium-intracellulare infection exhibited remarkable erythrophagocytotic activity and may represent an end-stage phenotype. They were positive for S100 protein and did not produce lysozyme or α-1-antichymotrypsin. They lost the antigen which was detected by monoclonal antibody Mac387 whereas positivity for HLA-DR, CD68 and KI-M8 was preserved. While many lymphocytes expressed CD25 (IL2 receptor) in cases with typical granulomas, there was no such CD25 expression in cases without epithelioid cell formation. Although granulomas have been produced in experimental animals independently of cell-mediated immune mechanisms, our results suggest that T-cell functions are necessary for epithelioid granuloma formation in human tuberculosis.

Resolution of acute malarial infections by T cell-dependent non-antibody-mediated mechanisms of immunity

While it is generally accepted that acute blood stage malarial infections are resolved through the actions of protective antibodies, we observed that resistance to acute infection with Plasmodium chabaudi adami was mediated by T cell-dependent cellular immune mechanisms independent of antibody. We now report that acute blood stage infections caused by three additional murine hemoprotozoan parasites, Plasmodium vinckei petteri, Plasmodium chabaudi chabaudi, and Babesia microti, appear to be controlled by similar T cell-dependent mechanisms of immunity. Mice rendered B cell deficient by lifelong treatment with goat anti-mouse immunoglobulin M (IgM) had IgM levels in serum of less than 0.6 micrograms/ml and contained precipitating amounts of goat anti-mouse IgM. When these B cell-deficient mice were infected with blood stage P. vinckei petteri, P. chabaudi chabaudi, or B. microti, they resolved their infections with kinetics similar to those seen in immunologically intact mice. Infected B cell-deficient mice did not produce antiparasite antibodies. As assayed by immunofluorescence, significant titers of parasite-specific antibody were present only in the sera of infected immunocompetent mice. In addition, only sera from infected immunocompetent mice immunoprecipitated metabolically labeled parasite antigens. In contrast to B cell-deficient mice, athymic nude mice failed to resolve acute P. vinckei petteri or B. microti infections. These data suggest that antibody-independent, T cell-mediated immune mechanisms play a more significant role in resisting acute blood stage infections caused by hemoprotozoa than was recognized previously.

Cell-mediated immunity to the asexual blood stages of malarial parasites: Animal models

Studies using experimental models of malaria in immunodeficient mice and chickens have shown that resistance to blood-stage infection is mediated by protective antibodies and T cell-dependent cell-mediated mechanisms of immunity. Depending on the infecting species of Plasmodium and prior experience of the host, either humoral or cell-mediated immune mechanisms predominate. Cell-mediated immunity has been adoptively transferred with CD4 + splenic T cells, and with antigen-specific T cell lines and clones. Since ascending parasitemia occurs in all instances, the transferred cells do not kill plasmodia directly but appear to activate effector mechanisms capable of destroying the invading parasites. Both CD4 + and CD8 + T cells were found to increase in the spleens of malarious mice. Depletion of CD4 + T cells prevented nude mice adoptively transferred with immune splenic T cells from clearing parasitemia. In contrast, late treatment with anti-CD4 antibody had little if any effect. The converse was true when anti-CD8 antibody was utilized, i.e., a significant number of mice treated with anti-CD8 antibody after parasitemia became patent and had difficulty clearing blood parasites. These data suggest that during infection CD8 + T cells may become activated by CD4 + T cells responding to malarial antigens. These CD8 + T cells may be directly cytotoxic or secrete additional cytokines thereby amplifying the role of CD4 + T cells in the activation of anti-parasite effector mechanisms. Finally, a hypothesis is presented to explain how the parasite in natural infections may activate T cell-dependent effector mechanisms in order to control its numbers in host tissues thereby ensuring the survival of both parasite and host.

Vascular Disease in Scleroderma: Endothelial T Lymphocyte-Fibroblast Interactions

The accumulated body of evidence suggests a role for a cell-mediated immune mechanism in the pathogenesis of scleroderma vascular disease. The most likely target for immune injury is either the endothelial cell itself or components of its basal lamina, which include type IV collagen and laminin. Whatever the specific target, the net effect is persistently altered endothelial cell dysfunction. However, the molecular basis for the development of endothelial cell injury is not known. Direct investigations of perivascular infiltrating cells have not been possible yet; published studies have focused on the in vitro effects of peripheral blood mononuclear cells and selected cytokines on endothelial cell behavior and function. Understanding the multiple cellular effects of various cytokines on endothelial cells may further the knowledge of the vascular disease. Systematic study of interactions between endothelial cells and cells of the immune system may provide the molecular basis for vascular injury and open yet unidentified avenues for therapy. Furthermore, monitoring parameters of endothelial cell injury may help to define the disease in an earlier and more meaningful fashion. Circulating levels of EC products such as von Willebrand factor, plasminogen activator, and prostacyclin/thromboxane metabolites may permit a precise definition of disease activity and assist the clinician in monitoring responses to therapy.

S-Antigen: preparation and characterization of site-specific monoclonal antibodies

Previous attempts to prepare monoclonal antibodies (MAbs) against S-antigen, a photoreceptor cell protein involved in the visual process and a potent autoantigen for the induction of experimental autoimmune uveitis (EAU), have yielded MAbs which define only carboxyl terminal epitopes. In this study we devised alternate strategies to prepare five MAbs directed to other regions of the molecule. MAbC10C10 and MAbH11-A2 were prepared against synthetic peptides known to be uveitopathogenic and they were selected for more detailed studies. MAbC10C10 was generated against synthetic peptide BSA281-302 which contains a predictive consensus sequence for defined T cell epitopes (GIALD) as well as a consensus sequence for GTP-binding proteins. One human adenosine deaminase synthetic peptide containing an extensive amino acid sequence homology to BSA281-302 was a potent inhibitor of MAbC10C10 binding in a competitive inhibition radioimmunoassay. MAbH11-A2 was generated against peptide BSA303-332 which also contains a uveitopathogenic site. The binding site of MAbH11-A2 was determined to be within amino acid positions 305 to 314 (NLASSTIIKE) in S-antigen. This binding site corresponded closely to the binding site of an affinity-purified rat polyclonal antibody raised to human S-antigen. MAb5C6.47 was isolated from a mouse hyperimmunized with bovine S-antigen and was specific for a highly conserved sequence near the amino terminus, amino acid residues 42 to 48 (DGVVLVD). Both MAbC10C10 and MAb5C.47 were useful in screening gt11 cDNA libraries expressing S-antigen polypeptides as fusion proteins. Our results demonstrate the feasibility of producing site-specific MAbs potentially useful in the study of T cell-mediated immune mechanisms in EAU as well as in the phototransduction of vision.

Immunological intercourse at the feto— maternal interface?

The immunological phenomena associated with pregnancy continue to intrigue and, at a recent meeting on the immunology of reproduction, several themes emerged. MHC expression by the trophoblast, maternal cell-mediated immune effector mechanisms and cytokine production at the feto-maternal interface were among the topics discussed.

Vesicular removal by oligodendrocytes of membrane attack complexes formed by activated complement.

Oligodendrocytes synthesize myelin in the central nervous system and maintain it in lamellar sheaths around axons. Techniques for studying oligodendrocyte development in vitro can be used, indirectly, to investigate the myelin injury that occurs in human and experimental demyelinating disease. Cell-mediated immune mechanisms are necessary but not sufficient to induce myelin damage in vivo; more recently complement has also been implicated in the pathogenesis both of multiple sclerosis and experimental allergic encephalomyelitis. Previously we have demonstrated that antibody-independent complement activation occurs in vitro at the oligodendrocyte surface. Here we show that the ensuing oligodendrocyte injury is reversible, and that recovery involves the release of membrane-attack complex-enriched vesicles from the surface of viable cells. The demonstration of morphologically and immunochemically identical vesicles in the cerebrospinal fluid of patients with multiple sclerosis suggests that reversible complement-mediated injury contributes to myelin damage in vivo.

Profile of human T cell response to leishmanial antigens. Analysis by immunoblotting.

Control and resolution of leishmanial infection depends primarily on T cell-mediated immune mechanisms. The nature of the leishmanial antigens involved in eliciting T cell immunity is unknown. We have examined the pattern of peripheral blood lymphocyte responses in patients with active, healed, or subclinical leishmanial infection to fractionated leishmanial antigens using a T cell immunoblotting method in which nitrocellulose-bound leishmanial antigen, resolved by one or two dimensional electrophoresis, are incorporated into lymphocyte cultures. The proliferative and IFN-gamma responses of cells from patients with healed mucosal or cutaneous leishmaniasis were remarkably heterogeneous and occurred to as many as 50-70 distinct antigens. In contrast, responses from subjects with active, nonhealing, diffuse cutaneous leishmaniasis were either absent or present to only a small number of antigens. Control and resolution of leishmaniasis, and resistance to reinfection, is therefore associated with a T cell response to a large and diverse pool of parasite antigens. The method of T cell immunoblotting appears to offer a powerful, rapid, and relatively simple approach to the identification of antigens involved in eliciting a T cell response in human leishmaniasis.

Immunology and Immunoregulation of Parasitic Hematozoan Infections

The hematozoan parasites comprise a medically important group of organisms which have received increasing attention in recent years. Malaria, particularly, has garnered significant research effort in regards to the development of sporozoite-specific vaccines. However, initial enthusiasm for an effective vaccine has been dampened as a result of field studies showing the presence of surface epitope-specific antibodies in drugcured and subsequently reinfected patients. Of importance, increasing evidence exists that cell-mediated immune mechanisms may play a central role in protection and pathogenesis in malaria. New evidence to unravel the mechanisms and significance of immunosuppression in leishmaniasis and Chagas' disease continues to implicate a complex circuit involving suppressor macrophages, lymphokine deficiencies, and atypical behavior of T helper cell populations. The African trypanosomes provide the cellular and molecular biologists challenges in understanding the basis and regulation of variant-specific glycoproteins (VSG) and their significance in immunity and pathogenesis. An important recent determination is that there appears to be little or no correlation between expression of a specific VSG and pathogenesis. The present status of research on the hematozoan parasites reestablishes the remarkable evolutionary accomplishments of these organisms to survive in the hostile immune environment of their vertebrate hosts.

Altered expression of the Salmonella typhimurium-specific B-cell repertoire in mice chronically treated with antibodies to immunoglobulin D

Using a modification of the splenic focus assay, we analyzed the Salmonella typhimurium-specific B-cell repertoire in salmonella-susceptible BALB/c mice. Although these mice normally succumbed to salmonella infection before antibody was produced, they appeared to have splenic S. typhimurium-specific B-cell precursors that could be activated to differentiate and secrete antibody in a manner which was quantitatively and qualitatively identical to that of salmonella-resistant mouse strains. We also analyzed the primary S. typhimurium-specific B-cell repertoire in BALB/c mice that had been chronically treated with antibodies to immunoglobulin D (IgD) and therefore had no surface IgD-positive B cells. Although the frequency of S. typhimurium-specific precursors in these mice was similar to that of control mice, there was an apparent alteration in the isotype distribution pattern in anti-IgD-treated mice. Control mice generated a significantly greater proportion of IgG-secreting clones than did anti-IgD-treated mice. In addition, a greater proportion of S. typhimurium-specific clones from control mice secreted IgG2 than secreted IgG1, and those clones that secreted IgG2 but not IgM, IgG3, or IgG1 were greater than 20-fold more common in control than in anti-IgD-treated mice. Finally, we analyzed the immune response of control and anti-IgD-treated mice to a live avirulent vaccine, S. typhimurium SL3235. Although both groups were protected after challenge with a live virulent S. typhimurium strain, only the control mice made serum antibodies to this vaccine. Taken together, these results show that (i) salmonella-susceptible BALB/c mice have S. typhimurium-specific B cells, (ii) the S. typhimurium-specific B cells in anti-IgD-treated mice may have a restricted capacity to switch heavy-chain classes, (iii) the similarity observed in the frequency of the S. typhimurium-specific precursors for these two groups of BALB/c mice is not reflected in the serum, and (iv) the failure of anti-IgD-treated mice to generate a serum antibody response to SL3235 in the face of complete protection suggests that this model may be used to study cell-mediated immune mechanisms in the apparent absence of humoral immunity.

Intestinal Lymphocyte Populations and Mechanisms of Cell-Mediated Immunity

Intestinal Lymphocyte Populations and Mechanisms of Cell-Mediated Immunity

Acute Interstitial Nephritis: Immunologic and Clinical Aspects

Acute interstitial nephritis is a common renal syndrome that may be associated with a variety of infections and drug therapies or may develop without an identified cause. Three cases are presented to illustrate the three types of acute interstitial nephritis--drug related, infection related, and idiopathic. Cell-mediated immune mechanisms seem to be more important than humorally mediated mechanisms in the pathogenesis of acute interstitial nephritis. Frequently, eosinophils are identified as a component of the interstitial cellular infiltrate, and eosinophiluria and eosinophilia have been claimed to be helpful in the diagnosis of acute interstitial nephritis, especially the drug-induced type. Neither eosinophiluria nor the presence of increased urinary levels of eosinophil major basic protein, however, is specific for the diagnosis of acute interstitial nephritis. Patients with drug-induced interstitial nephritis frequently have symptoms and signs suggestive of a hypersensitivity syndrome and rarely have more dramatic anaphylactic manifestations. Systemic glucocorticoids have been shown to be beneficial in this type of acute interstitial nephritis.

Urinary neopterin levels in acute viral hepatitis.

Elevated neopterin levels in blood or urine have been shown to be a marker for the activation of cell-mediated immunity in vitro and in vivo. To evaluate whether neopterin levels are elevated in patients with acute viral hepatitis, we measured urinary levels in 13 patients with hepatitis A, 26 with hepatitis B, 12 with non-A, non-B hepatitis, 8 with jaundice and/or cholestasis due to biliary and pancreatic disorders and 3 with alcoholic hepatitis and in 62 apparently healthy HBsAg carriers. Neopterin levels in patients with virus-induced hepatitis were significantly higher than those in patients with other diagnoses. Urinary neopterin levels were above normal in 49 of 51 patients with viral hepatitis and elevations during the course of hepatitis showed a pattern similar to that of the usual liver biochemical tests, suggesting that neopterin levels were related to the clinical activity of the viral disease. In patients with nonviral biliary and hepatic disorders, neopterin levels were usually normal and did not correlate with other liver biochemical tests. These findings suggest that cell-mediated immune mechanisms are activated during viral hepatitis and that neopterin measurement may be of value as an additional surrogate marker for non-A, non-B hepatitis.

Cytokine production in patients with newly diagnosed insulin-dependent (type I) diabetes mellitus.

There is ample evidence that cell-mediated immune mechanisms are crucial in the initiation of insulin-dependent diabetes mellitus (IDDM). Therefore, the role of cytokines in the pathogenesis of IDDM was investigated in 51 patients with IDDM, in comparison with 20 normal controls. The patients were divided into three groups, group 1 consisting of 31 newly diagnosed type 1 diabetics, in group 2 IDDM had been diagnosed for between 2 months and 2 years, and in group 3 onset had occurred 2-20 years before. Interleukin 1 (IL 1) activity was measured by the thymocyte co-stimulator assay, and interleukin 2 (IL 2) using IL 2 dependent cell lines. Peripheral blood monocyte IL 1 production was not altered under basal conditions. However, silica-stimulated IL 1 release was normal in patients with newly diagnosed or short-term disease, but was significantly decreased in long-term diabetics. Peripheral blood T-lymphocyte IL 2 production at onset of IDDM was normal under basal conditions, and upon optimal stimulation with concanavalin A (ConA) and phorbol myristate acetate (PMA). However, in the two groups with longer standing diabetes, basal and stimulated IL 2 release was decreased. We conclude that monocytes and T-lymphocytes from patients with diabetes mellitus have a diminished capacity to release IL 1 and IL 2 only later in the course of the disease. At the time of manifestation of disease, IL 1 and IL 2 production is normal in type-I diabetes mellitus.

Resolution of chlamydial genital infection in B-cell-deficient mice and immunity to reinfection.

The purpose of this investigation was to determine the relative roles of the humoral and cell-mediated immune responses in the resolution of chlamydial genital infection of mice and resistance to reinfection. To this end, female BALB/c mice were rendered B cell deficient by treatment with heterologous anti-immunoglobulin M (IgM) serum from birth. Controls were similarly treated with either normal serum or phosphate-buffered saline. Before inclusion in each experiment, anti-IgM-treated mice were screened for the absence of IgM in serum and for the presence of cell-mediated immune responses. In addition, spleen cells from anti-IgM-treated mice responded to concanavalin A and phytohemagglutinin but not to lipopolysaccharide. By these criteria, mice were designated B cell deficient. B-cell-deficient mice and controls were inoculated intravaginally with a suspension of mouse pneumonitis agent (MoPn), a Chlamydia trachomatis biovar. All B-cell-deficient mice resolved the infection. Additionally, no significant difference was seen in the course of the infection in B-cell-deficient mice when compared with controls. In contrast to control mice, B-cell-deficient mice displayed no detectable antibody responses to MoPn in serum or in genital secretions. However, both B-cell-deficient mice and controls developed delayed-type hypersensitivity and T-cell proliferative responses to MoPn. When challenged 53 days after primary infection, no significant difference was seen in the resistance of B-cell-deficient mice to reinfection when compared with that of the controls. These data indicate that cell-mediated immune mechanisms play an important role in the resolution of and resistance to chlamydial genital infection in this model.

The influence of adjuvant on induction of protective immunity by a non-living vaccine against schistosomiasis.

Mice were protected against subsequent infection with Schistosoma mansoni by intradermal or s.c. vaccination with killed schistosomula or soluble parasite extracts and bacillus Calmette-Guérin (BCG). Treatment with i.p. immunization was somewhat less effective, whereas i.m. vaccination failed to elicit protective immunity. The level of resistance induced by intradermal immunization was influenced by the strain of BCG used, and isolated BCG cell walls did not reliably substitute for whole BCG organisms as adjuvant. Bordetella pertussis vaccine and saponin were also able to function as adjuvants for protective immunity in this model, whereas other immunopotentiators including Corynebacterium parvum and aluminum hydroxide were ineffective. No correlation between resistance to challenge infection and antibody levels was detected. Animals immunized intradermally using either protective or non-protective adjuvants all showed minimal humoral reactivity against schistosomulum surface Ag but strong IgG response to soluble parasite components including paramyosin, which is the major serologically recognized Ag in mice vaccinated intradermally with schistosome Ag plus BCG and is protective in this model. In contrast, a strong correlation was observed between resistance and Ag-specific cell-mediated reactivity, including IFN production by T lymphocytes in vitro and macrophage activation in vivo. These results further substantiate the hypothesis that protection in this model is based on cell-mediated immune effector mechanisms. Moreover, they may be of general relevance in the design of vaccination protocols using other Ag or against other infectious agents.

Adoptive protection against Plasmodium chabaudi adami malaria in athymic nude mice by a cloned T cell line.

T cell-dependent, cell-mediated immune mechanisms have been shown to contribute to resistance against malaria. Because the identity of plasmodial Ag responsible for the activation of these protective immune responses remains unknown, a major step in isolating these potential immunizing agents will be the development of adequate screening procedures designed to identify important T cell Ag. This study focused on the isolation of protective T cell clones that may play a pivotal role in this process. A T cell clone designated CTR2.1 and two subclones derived from it adoptively transferred protection to athymic nude mice infected with Plasmodium chabaudi adami, a murine malarial parasite known to be recognized by protective thymus-dependent immune mechanisms. The protective T cell clone displayed a L3T4+, Lyt-2- surface phenotype and secreted both IFN-gamma and IL-2 after stimulation with solubilized parasites in vitro. This is the first report of results demonstrating a cloned T cell line capable of providing adoptive protection against malaria in vivo. More importantly, CTR2.1 and other protective T cell clones may provide for the identification of plasmodial antigenic epitopes recognized by important cell-mediated immune mechanisms during acute malarial infection.

Immunological Functions of the Gut–Role of the Mucosal Immune System

This review summarizes recent information about immune responses in the intestinal mucosa with emphasis on the role of orally-administered antigens from the external environment. The intestinal mucosa provides an extensive surface for potential absorption of pathogenic environmental antigens, such as microbes, chemicals, and food. The intestinal mucosa is densely populated by IgA-producing plasma cells. The humoral immune responses to antigens in the intestinal mucosa are largely of the IgA class in secretory form (sIgA). This sIgA provides an immunological barrier to absorption of antigens on the mucosal epithelium and to penetration into the body. The cell-mediated immune mechanism is also equipped in the mucosal sites. In addition, the mucosal immune response induces hyporesponsiveness of nonmucosal (systemic) immune reactions, and the liver is an integral part of the mucosal immune system. Thus we consider that the mucosal immune system plays a central role in the maintenance of the homeostasis of the total immune system.

The relationship of infiltrating renal leucocytes to disease activity in lupus and cryoglobulinaemic glomerulonephritis.

In order to evaluate the contribution of cellular immune mechanisms in the pathogenesis of immune complex-mediated glomerulonephritis, renal biopsies from 18 patients with lupus glomerulonephritis and 26 with cryoglobulinaemic glomerulonephritis were studied. Leucocyte profiles including T cell subsets and 'activated' macrophages within both glomeruli and interstitium were determined, using a panel of monoclonal antibodies as markers, and a sensitive 4-layer peroxidase technique to localize these within tissues. The infiltrating leucocytes were correlated with clinical, histological and immunological parameters of disease activity. Normal glomeruli contained few leucocytes though normal interstitium did (145 +/- 30 mm2), made up predominantly of T lymphocytes and macrophages. There was a significant increase in intraglomerular leucocytes in both systemic lupus erythematosus 4-fold, and essential mixed cryoglobulinaemia 7-fold, as compared to normal. These leucocytes consisted mainly of macrophages, and particularly in cryoglobulinaemia of 'activated' macrophages as demonstrated by their surface expression of the procoagulant tissue factor recognized by the A13 monoclonal antibody. In cryoglobulinaemic glomerulonephritis (GN) there was also a significant increase in T lymphocytes due to a predominance of suppressor-cytotoxic cells (OKT8+). There was a significant increase in interstitial leucocytes in both diseases, lymphocytes (mainly OKT8+ve), and macrophages (mainly 'activated' A13+ve). There were significant positive correlations between disease activity and interstitial leucocyte infiltration including, in lupus nephritis, degree of proteinuria and total leucocytes, hypocomplementaemia and T lymphocytes, increased numbers of monocytes and lymphocytes with a higher histological index of activity, and in cryoglobulinaemic GN of T lymphocytes and proliferative lesions, and T lymphocytes and C1q deposition. This study has demonstrated the importance of the interstitium in the pathogenesis of both diseases, delineated the presence of both T lymphocytes and activated monocytes which make cell-mediated immune mechanisms feasible, and linked the presence of immune mediators to disease activity.

Immunopathogenetic Mechanisms in Renal Disease

This review deals with various immunopathogenetic mechanisms of renal diseases. Although immune-complex nephritis was long thought to be the result of deposition of circulating immune complexes, recent studies have revealed the importance of in situ formation. In experimental Heymann nephritis, an antigen (gp 330) has been localized on glomerular epithelial cells, and antibodies reactive with gp 330 have been eluted from glomeruli; deposits appear to result from shedding of complexes from the podocyte surface into the basement membrane. In human disease, it seems likely that mesangial and subendothelial deposits most often result from deposition of circulating immune complexes, whereas subepithelial deposits are formed mainly in situ. Cell-mediated immune mechanisms are capable of producing glomerular injury, as shown in experimental models. In humans, Wegener's granulomatosis and idiopathic crescentic glomerulonephritis may involve such mechanisms. In certain forms of experimental and human tubulointerstitial nephritis, cell-mediated immunity also seems to play an important role.