Parasite immunology and lymphocyte population dynamics

We propose that parasites use "antigenic mimicry", the presentation of host-type antigens, not merely as a disguise, but as a means of actively diverting the immune system into an ineffective mode of response that actually protects the parasites. This suggestion is the outcome of analyzing the immune system by the principle of Darwinian selection--among lymphocyte populations differing in their relative growth capacities under particular environmental conditions. In particular, it is proposed that proliferation can be uncoupled from differentiation under certain predictable conditions; and moreover, clones that proliferate for prolonged periods of time without significant maturation into effector cells may gain a selective advantage and reach prominence. This mode of "latent proliferation" is a key to self-non-self discrimination: under physiologic conditions, those T and B cells are selected that react "proliferatively" with certain classes of self-antigens, ensuring tolerance to self. We suggest that parasites which present host-type antigens generate the same kind of dynamic selection among responding lymphocytes. The hypothesis links polyclonal activation and "immunosuppression" to "antigenic mimicry", predicts "concomitant immunity" to the same parasite and suggests a pathway leading to autoimmunity. It is also amenable to testing.

Experimental autoimmune encephalomyelitis mediated by T lymphocyte lines: genotype of antigen-presenting cells influences immunodominant epitope of basic protein

Lewis rats are susceptible to experimental autoimmune encephalomyelitis (EAE), and their T lymphocytes recognize epitopes in the 68-88 sequence of guinea pig myelin basic protein (BP). BN rats are resistant to EAE, and their T lymphocytes recognize epitopes outside of the 68-88 sequence, probably in the 43-67 portion of BP. To investigate the influence of the genome of antigen-presenting cells (APC) on the dominance of BP epitopes for T lymphocyte lines, we selected anti-BP lines from (Lewis X BN)F1 rats by using the APC of Lewis, BN, or F1 origin. We now report that the F1/Lewis and F1/F1 lines recognized the 68-88 epitopes and were highly encephalitogenic in F1 rats, whereas the F1/BN line recognized the 43-67 epitopes and was only weakly encephalitogenic. Thus, the genotype of the APC can influence the immunologic dominance for T lymphocytes of BP epitopes, and this dominance in turn can influence the expression of disease.

A human monoclonal antibody to insulin

To elucidate the immune aspects of insulin-dependent diabetes mellitus (IDDM), we attempted to generate human monoclonal anti-insulin antibodies by fusing peripheral blood lymphocytes obtained from 10 insulin-treated IDDM patients with cells from a human lymphoblastoid cell line. Hybridomas that secreted immunoglobulins appeared in 9 of 400 wells. One of these hybridomas secreted anti-insulin antibody of the IgM class. The lymphocytic partner of this hybridoma was obtained from an IDDM patient who had undetectable levels of antibodies to insulin in his serum. Thus, by employing the hybridoma technique, it was possible to reveal the presence of insulin-sensitized B-lymphocytes in a patient who was serologically negative for anti-insulin antibodies. The monoclonal antibody recognized intact human insulin and insulins of other species, but not isolated A- and B-chains. This indicates that the antibody was functionally an autoantibody directed to an epitope formed by the native conformation of a highly conserved portion of the insulin molecule. This is the first report of a human hybridoma antibody to insulin.

Arthritis induced by a T-lymphocyte clone that responds to Mycobacterium tuberculosis and to cartilage proteoglycans

Adjuvant arthritis characterized by chronic inflammation of the joints of rats is induced by immunization to Mycobacterium tuberculosis. To learn how autoimmune arthritis may be caused by a microbial antigen, we isolated a T-lymphocyte clone specific for M. tuberculosis antigens that was strongly arthritogenic. We now report that the clone recognized, in addition to M. tuberculosis antigens, antigens present in human synovial fluid, medium of chondrocyte cultures, and proteoglycans purified from cartilage. These observations indicate that the target antigen for the arthritogenic clone resides in the proteoglycan component of cartilage. As this arthritogenic clone shows specificity for both a M. tuberculosis antigen and a cartilage constituent we conclude that disease is probably caused by antigenic cross-reactivity. Thus, an autoimmune disease may be triggered by structural mimicry between antigens in the environment and self-antigens in the individual.

T lymphocyte clones and experimental autoimmune diseases

This article reviews some of the lessons derived from our use of T lymphocyte lines and clones to study three experimental autoimmune diseases: experimental autoimmune encephalomyelitis, experimental autoimmune thyroiditis and adjuvant arthritis. In each of these disease models we have raised lines and clones of T lymphocytes of the helper phenotype that are specifically autoimmune. These T lymphocytes were used to investigate the pathogenesis of disease. Lines and clones were also exploited to induce resistance to disease.

Specificity of T lymphocyte lines for peptides of myelin basic protein

T lymphocyte lines specific for myelin basic protein (BP) can mediate experimental autoimmune encephalomyelitis (EAE), or can protect against the active induction of the disease. To investigate the antigenic fine specificity of guinea pig (GP) BP-specific T cell lines raised from different rat strains, and to determine whether functionally different T lymphocyte lines and clones recognized the same or different regions of the BP molecule, the proliferation responses of line cells were assessed after stimulation with purified peptides of GP-BP. Lewis rat T cell lines and clones selected for responses to whole GP-BP responded selectively to the 68-88 amino acid sequence of GP-BP, but not to the 1-37, 43-67, or 89-169 sequences. The region of GP-BP recognized by Lewis T cells was additionally defined to include the 75-80 amino acid sequence, because a T cell clone responded equally to GP and rat BP which differed by only one amino acid at position 79, but did not respond to human or bovine BP, which had a Gly-His insertion in this region. T lymphocyte lines derived from the F344 and PVG (Weizmann) rat strains shared the same selective response to peptide 68-88, but lines from BN rats responded to an epitope(s) outside of the 68-88 sequence. The functional capacity of the various T cell lines to mediate experimental autoimmune encephalomyelitis (EAE) or to induce resistance against EAE was independent of their specificity for the different GP-BP peptides; lines specific for epitope(s) within or excluded from the 68-88 sequence could be encephalitogenic depending on their strain of origin, and various lines specific for the 68-88 peptide could induce both disease and protection, disease only, or neither activity.

The study and manipulation of experimental autoimmune disease using T lymphocyte lines

Autoimmune diseases include entities of varied clinical expression such as juvenile onset diabetes mellitus, rheumatoid arthritis, multiple sclerosis, and thyroiditis. Nevertheless, these autoimmune diseases have a common origin; they are caused by clones of lymphocytes that specially attack the individual's own body components. To study autoimmune processes, we have isolated and grown as long-term cell lines the T lymphocytes that mediate several different experimental autoimmune diseases in rats or mice. These cell lines have increased our understanding of pathogenesis, but perhaps more importantly, it appears that suitably attenuated lines can be used to immunize the individual animal against its own autoimmune cells. Thus, autoimmune cells can be used as vaccines to prevent or treat the autoimmune process.

Specificity of T lymphocyte lines for peptides of myelin basic protein

T lymphocyte lines specific for myelin basic protein (BP) can mediate experimental autoimmune encephalomyelitis (EAE), or can protect against the active induction of the disease. To investigate the antigenic fine specificity of guinea pig (GP) BP-specific T cell lines raised from different rat strains, and to determine whether functionally different T lymphocyte lines and clones recognized the same or different regions of the BP molecule, the proliferation responses of line cells were assessed after stimulation with purified peptides of GP-BP. Lewis rat T cell lines and clones selected for responses to whole GP-BP responded selectively to the 68-88 amino acid sequence of GP-BP, but not to the 1-37, 43-67, or 89-169 sequences. The region of GP-BP recognized by Lewis T cells was additionally defined to include the 75-80 amino acid sequence, because a T cell clone responded equally to GP and rat BP which differed by only one amino acid at position 79, but did not respond to human or bovine BP, which had a Gly-His insertion in this region. T lymphocyte lines derived from the F344 and PVG (Weizmann) rat strains shared the same selective response to peptide 68-88, but lines from BN rats responded to an epitope(s) outside of the 68-88 sequence. The functional capacity of the various T cell lines to mediate experimental autoimmune encephalomyelitis (EAE) or to induce resistance against EAE was independent of their specificity for the different GP-BP peptides; lines specific for epitope(s) within or excluded from the 68-88 sequence could be encephalitogenic depending on their strain of origin, and various lines specific for the 68-88 peptide could induce both disease and protection, disease only, or neither activity.

Role of the thymus in induction and transfer of vaccination against adjuvant arthritis with a T lymphocyte line in rats

Adjuvant arthritis is an experimental disease of rats induced by immunization to antigens of Mycobacterium tuberculosis. Our observation that arthritis could be induced in irradiated rats by the A2 line of T lymphocytes in the absence of mycobacterial antigens suggested that adjuvant arthritis is an autoimmune disease. Moreover, the A2 line could be used to vaccinate unirradiated rats against the subsequent induction of adjuvant arthritis by active immunization to Mycobacteria. In the present study we found that thymus cells obtained from A2 vaccinated rats could transfer resistance to adjuvant arthritis to naive rats. This indicates that the mechanism of resistance induced by A2 vaccination is probably immunological and involves thymus-derived lymphocytes.

Autoimmune T-lymphocytes with specificity for pancreatic islet antigens

The question is still unresolved whether in insulin-dependent (type I) diabetes T-lymphocytes mediate an autoimmune response towards pancreatic islets. We now present direct evidence in an animal model for autoimmune T-lymphocytes with specificity for islet antigens. Mice of strain C57BL/6 were immunized repeatedly with islet homogenates. Lymphocytes isolated from draining lymph nodes and the spleen show a specific proliferative response when challenged with mouse rat or islet antigens but do not respond to liver or spleen antigens. Islet antigen specific lymphoblasts have been maintained by in vitro culture for several weeks in the presence of T-cell growth factor containing medium.

T lymphocyte lines induce autoimmune encephalomyelitis, delayed hypersensitivity and bystander encephalitis or arthritis

Lines of rat T lymphocytes responsive to the basic protein of myelin (BP) or to the purified protein derivative of Mycobacterium tuberculosis (PPD) were inoculated i.v. into recipient rats. As reported previously, the anti-BP line cells, but not the anti-PPD line cells spontaneously accumulated in the central nervous system and caused encephalomyelitis. However, the anti-PPD line cells could be induced to enter the brain and cause bystander encephalitis by intracerebral inoculation of PPD. Anti-PPD or anti-BP line cells could mediate delayed-type hypersensitivity skin reactions or bystander arthritis elicited by specific antigen. The lines did not cause specific cytolysis in vitro. Susceptibility to delayed-type hypersensitivity or bystander disease was long lasting in rats inoculated with anti-PPD line cells, while rats inoculated with anti-BP line cells were susceptible for only a few days. Thus, lines of T lymphocytes can mediate a variety of pathological reactions directed by the presence of specific antigen, self or foreign.

Activated T lymphocytes produce a matrix-degrading heparan sulphate endoglycosidase

We have previously found that lines of activated T lymphocytes specifically autosensitized to the basic protein of myelin (BP), on intravenous inoculation into syngeneic rats, were able to penetrate blood vessels, accumulate in the nervous system and cause experimental autoimmune encephalomyelitis (EAE). An important question is how effector T cells reach such targets outside the walls of blood vessels. To investigate this we have studied in vitro the interaction of anti-BP effector T lymphocytes with the basement membrane-like extracellular matrix produced by vascular endothelial cells. We now report that activated but not resting T lymphocytes produce an endoglycosidase capable of degrading heparan sulphate side chains of the proteoglycan scaffold of the extracellular matrix. Moreover, the anti-BP T lymphocytes respond to BP presented by extracellular matrix by markedly enhanced elaboration of the endoglycosidase. These results suggest that tissue-specific antigens on blood vessel walls could direct lymphocyte homing by activating enzymes that facilitate penetration of the subendothelial basal lamina. They also suggest that effector T lymphocytes can recognize antigen which is not associated with a major histocompatibility complex signal.

Mouse antibodies to the insulin receptor developing spontaneously as anti-idiotypes. I. Characterization of the antibodies

Mice immunized to ungulate insulins were found to develop antibodies of two specificities: insulin antibodies that were mostly IgG1 and IgG2 antibodies that acted both as anti-idiotypes to specific mouse insulin antibodies and as antibodies to the insulin receptor. There was a negative association between the presence of anti-idiotypic receptor antibodies and insulin antibodies bearing the specific idiotype; the specific idiotypic antibodies were confined to the early phase of the primary response while the anti-idiotypic receptor antibodies were detected only after the idiotypic antibodies had disappeared. To map the insulin epitope that triggered the specific idiotypic response, we chemically altered the insulin molecule so as to inhibit its interaction with the insulin receptor. The altered insulins triggered high titers of antibodies binding to antigenic determinants on native insulin, but no anti-idiotypic receptor antibodies. Thus, the epitope responsible for the specific idiotypic-anti-idiotypic network was probably the part of the insulin molecule whose conformation is recognized by the insulin receptor.

Mouse antibodies to the insulin receptor developing spontaneously as anti-idiotypes. II. Effects on glucose homeostasis and the insulin receptor

Mice immunized to bovine insulin were observed to develop anti-idiotypic antibodies which behaved in in vitro assays as antibodies to the insulin receptor. The studies described here were undertaken to investigate the effects of these antibodies in vivo on the physiology of glucose homeostasis and the state of insulin receptors. Mice developing anti-idiotypic receptor antibodies manifested abnormal fasting blood glucose concentrations: a period of hypoglycemia followed by a period of hyperglycemia. Moreover, the mice were deficient in their ability to respond to a glucose load. Changes in the number and activity of insulin receptors were associated with these physiological aberrations. In an insulin binding assay, adipocytes obtained from immunized mice had only 40% of the number of insulin receptors demonstrable on the adipocytes of control mice. The lipogenic response of the affected adipocytes was also relatively insensitive to insulin, and in addition, they manifested only 70% of the maximal response to high concentrations of insulin. Thus, development of anti-idiotypic receptor antibodies appeared to be associated with insulin resistance of adipocytes and abnormal glucose homeostasis.

Immunological expression of gangliosides in multiple sclerosis and in a demyelinating model disease in rabbits

Accumulating evidence suggests that the process of demyelination in MS might involve an autoimmune response to one or more myelin components. A combination of myelin basic protein and myelin haptens was considered as possibly enhancing a cellular or humoral autoimmune reaction in MS. In line with this motion we have used an in-vitro E-rosette assay that correlates with in-vivo delayed hypersensitivity to demonstrate specific immunologic sensitivity of lymphocytes from MS patients to polysialogangliosides. A recent report that only lymphocytes from patients in relapse, but not in remission, are primed by gangliosides, underscores the relevance of the antigenic expression of gangliosides during the active pathological phase of the disease. The antigenic capacity of gangliosides to induce upon immunization a neurological disorder featured by demyelination in the CNS was demonstrated in rabbits. This and previous reports on the induction of peripheral demyelination in rabbits immunized with gangliosides will be further analyzed to gain insight on the possible role of these myelin lipid components as targets for an autoimmune mechanism in MS.

Arthritis induced in rats by cloned T lymphocytes responsive to mycobacteria but not to collagen type II

We have been studying the pathogenesis of adjuvant arthritis in rats using a long-term cell line of T lymphocytes, the A2 line, which can induce polyarthritis and can also be used to vaccinate rats against adjuvant arthritis. Although line A2 was selected for its proliferative response to mycobacteria, it also responded to collagen type II. To elucidate its role of responsiveness to collagen type II and the relationship between arthritogenicity and vaccination, we cloned A2 and selected a subline A2b. We now report that subline A2b, which bore a marker of helper/delayed hypersensitivity T lymphocytes, was strongly arthritogenic, but could not vaccinate against arthritis. Moreover, A2b showed no response to collagen type II. Therefore, reactivity to collagen type II is not a requisite for arthritogenicity, and mediation of arthritis and vaccination can be distinct properties of different populations of T lymphocytes.

Autoimmune encephalomyelitis (EAE) mediated or prevented by T lymphocyte lines directed against diverse antigenic determinants of myelin basic protein. Vaccination is determinant specific

Lines of T lymphocytes reactive against the basic protein of myelin (BP) were found in previous studies to mediate experimental autoimmune encephalomyelitis (EAE) in rats. Moreover, inoculation of rats with attenuated anti-BP line cells vaccinated them against subsequent attempts to induce active EAE by injection of BP in adjuvant. In the present study, we investigated the effects of T lymphocyte lines reactive to different antigenic determinants on the BP molecule, they are the major encephalitogenic peptide (EP) determinant present on guinea pig BP (G-BP), and minor, non-EP determinants present on bovine BP (B-BP). We found that both lines of T lymphocytes could mediate EAE. Resistance to active EAE acquired by spontaneous recovery from line mediated EAE or by vaccination with attenuated cells, however, was found to be specific for the particular BP determinant. Thus, EAE may be mediated by lines of T lymphocytes reactive to different determinants on the BP molecule, but the resistance to EAE acquired by exposure to line cells is determinant specific. This suggests that acquired resistance to EAE is directed by the receptor specificity of the autoimmune anti-BP T cells.

Autoimmune encephalomyelitis (EAE) mediated or prevented by T lymphocyte lines directed against diverse antigenic determinants of myelin basic protein. Vaccination is determinant specific

Lines of T lymphocytes reactive against the basic protein of myelin (BP) were found in previous studies to mediate experimental autoimmune encephalomyelitis (EAE) in rats. Moreover, inoculation of rats with attenuated anti-BP line cells vaccinated them against subsequent attempts to induce active EAE by injection of BP in adjuvant. In the present study, we investigated the effects of T lymphocyte lines reactive to different antigenic determinants on the BP molecule, they are the major encephalitogenic peptide (EP) determinant present on guinea pig BP (G-BP), and minor, non-EP determinants present on bovine BP (B-BP). We found that both lines of T lymphocytes could mediate EAE. Resistance to active EAE acquired by spontaneous recovery from line mediated EAE or by vaccination with attenuated cells, however, was found to be specific for the particular BP determinant. Thus, EAE may be mediated by lines of T lymphocytes reactive to different determinants on the BP molecule, but the resistance to EAE acquired by exposure to line cells is determinant specific. This suggests that acquired resistance to EAE is directed by the receptor specificity of the autoimmune anti-BP T cells.

T lymphocyte line specific for thyroglobulin produces or vaccinates against autoimmune thyroiditis in mice

We investigated Ly-1+ T lymphocyte line cells specifically reactive to thyroglobulin (Tg) that were isolated from mice primed with mouse Tg in adjuvant. Intravenous inoculation of as few as 10(5) line cells was sufficient to cause severe and prolonged thyroiditis in recipient mice that were intact, irradiated, or athymic nudes. Disease was independent of circulating Tg antibodies, suggesting that anti-Tg T lymphocytes could cause thyroiditis unaided by antibodies. Thyroiditogenic T lymphocytes could be isolated as cell lines from apparently healthy mice that had been immunized with non-thyroiditogenic bovine Tg in adjuvant, which indicates that autoimmune effector T lymphocytes may develop covertly in the course of immunization with foreign antigens. Finally, a single i.v. inoculation of anti-Tg T lymphocyte line cells attenuated by irradiation vaccinated mice completely against subsequent development of autoimmune thyroiditis produced either by active immunization to Tg or by passive transfer of intact line cells. Vaccinated mice that were protected from inflammatory lesions of thyroiditis still produced high titers of Tg antibodies in response to active immunization. Thus, vaccination specifically inhibited thyroiditogenic T lymphocytes but not helper T lymphocytes required for the production of Tg autoantibodies.

T lymphocyte line specific for thyroglobulin produces or vaccinates against autoimmune thyroiditis in mice

We investigated Ly-1+ T lymphocyte line cells specifically reactive to thyroglobulin (Tg) that were isolated from mice primed with mouse Tg in adjuvant. Intravenous inoculation of as few as 10(5) line cells was sufficient to cause severe and prolonged thyroiditis in recipient mice that were intact, irradiated, or athymic nudes. Disease was independent of circulating Tg antibodies, suggesting that anti-Tg T lymphocytes could cause thyroiditis unaided by antibodies. Thyroiditogenic T lymphocytes could be isolated as cell lines from apparently healthy mice that had been immunized with non-thyroiditogenic bovine Tg in adjuvant, which indicates that autoimmune effector T lymphocytes may develop covertly in the course of immunization with foreign antigens. Finally, a single i.v. inoculation of anti-Tg T lymphocyte line cells attenuated by irradiation vaccinated mice completely against subsequent development of autoimmune thyroiditis produced either by active immunization to Tg or by passive transfer of intact line cells. Vaccinated mice that were protected from inflammatory lesions of thyroiditis still produced high titers of Tg antibodies in response to active immunization. Thus, vaccination specifically inhibited thyroiditogenic T lymphocytes but not helper T lymphocytes required for the production of Tg autoantibodies.

Autoantibodies to the insulin receptor in juvenile onset insulin-dependent diabetes

Insulin-dependent diabetes mellitus (IDDM) usually begins in childhood or early adulthood, and its aetiology is thought to involve autoimmune damage to the islet cells that secrete insulin. To investigate an additional target of autoimmunity in IDDM we examined sera for antibodies to insulin receptors. Such antibodies were defined by their ability to compete with insulin for binding to insulin receptors and by their capacity to behave like insulin in activating lipogenesis in adipocytes. We now report the occurrence of anti-insulin receptor antibodies of the IgM class in the sera of 10 of 22 IDDM patients obtained before their treatment with exogenous insulin. Furthermore, two of five IDDM patients who were initially negative developed anti-insulin receptor antibodies during treatment with human or pork insulin. These findings suggest that autoimmunity to the insulin receptor may contribute to the pathophysiology of IDDM.

Immunospecific inhibition of nerve conduction by T lymphocytes reactive to basic protein of myelin

Experimental autoimmune encephalomyelitis (EAE) induced by immunization to the basic protein of central nervous system myelin (BP) is a paralytic disease in which T lymphocytes attack the individual's own central nervous system. As the target is in white matter, EAE has been considered an experimental model of some aspects of human disease such as multiple sclerosis. To investigate whether autoimmune T lymphocytes could produce paralysis, we studied the effects on the electrophysiology of isolated nerves produced by T-lymphocyte lines reactive specifically to BP or other antigens. We now report that propagation of action potentials evoked by electrical stimulation was blocked by incubating optic nerves with specific anti-BP T cells. This blockade could be reversed for up to two hours by removing the anti-BP line cells from the optic nerve. The anti-BP line cells had no effect on conduction along allogeneic optic nerves or syngeneic peripheral nerves. This indicates that disruption of the function of myelin in neuroimmunological disease may result from an immunologically specific interaction between autoimmune T lymphocytes and myelin antigens.

T lymphocyte lines producing or vaccinating against autoimmune encephalomyelitis (EAE). Functional activation induces peanut agglutinin receptors and accumulation in the brain and thymus of line cells

We studied lines of rat T cells, specifically reactive against myelin basic protein (BP), that were functional in mediating autoimmune encephalomyelitis or in vaccinating rats against induction of active EAE. Herein we report that these functions depended on activation of the cells by incubation with BP or with a T cell mitogen prior to inoculation into recipient rats. Activation was accompanied by the exposure of membrane-binding sites specific for the lectin peanut agglutinin. Accumulation of activated line cells in the central nervous system and thymus gland was observed.

Lines of T lymphocytes induce or vaccinate against autoimmune arthritis

The pathophysiology of autoimmune arthritis was studied by selecting and isolating lines of effector T lymphocytes from rats administered an arthritogenic dose of Mycobacterium tuberculosis in complete Freund's adjuvant to induce adjuvant arthritis. Irradiated rats were intravenously inoculated with a cell line characterized by proliferative reactivity to Mycobacterium tuberculosis and, to a lesser degree, to rat collagen type II. This produced arthritis in all the irradiated rats. Nonirradiated recipients failed to develop arthritis. However, such rats, and those recovering from cell-mediated arthritis, were resistant to subsequent attempts to induce adjuvant arthritis. Lines of T lymphocytes selected for responsiveness to other antigens had no effect. Therefore, a line of T lymphocytes responsive to bacteria or to collagen type II could either induce autoimmune arthritis or serve as an agent of vaccination against it.

Mice immunized to insulin develop antibody to the insulin receptor

We immunized mice with insulin and found that those strains that develop insulin antibodies subsequently produce insulin-like activity in amount equivalent to 300-400 ng insulin per ml serum. The activity was due exclusively to IgG2 antibodies. Bioactivity could be blocked efficiently by insulin antibodies from guinea pigs and from mice. The active IgG2 also displaced labeled insulin from fat cells. Preliminary in vivo studies have indicated that the appearance of insulin-like antibodies in the mouse resulted in abnormal glucose homeostasis and "down regulation" of insulin receptors. These results indicate that immunization to insulin can initiate an idiotype-anti-idiotype network resulting in antibodies to the hormone receptor.

Structural analysis of insulin determinants seen by T cells directed by H-2 genes

The magnitude of the immune response of lymphocytes to defined antigenic determinants of ungulate insulins is controlled by the products of H-2 genes. Based on the crystallographically solved structure of porcine insulin, the close homology of all the ungulate insulins, and the amino acid substitutions, we built models of the different insulins. We analyzed the likely conformations of the antigenic determinants, and proposed structural specificities accounting for the immunologic phenomena observed.

Molecular events in the processing of avidin by antigen-presenting cells (APC). III. Activation of T-lymphocyte lines and H-2 restriction are mediated by processed avidin associated with I-region gene products

We investigated the interaction between processed avidin (PA) and avidin-specific lines of T lymphocytes free of resident antigen-presenting cells (APC). We found that PA was able to replace the requirement for APC in the T-lymphocyte proliferative assay, only if the PA was associated with an Ia-positive moiety (IPM) supplied by the APC. In addition to supplying a necessary signal for a proliferative response to PA, IPM imposed H-2 restriction on the PA molecule. The association between PA and IPM was reversible and the two moieties could be physically separated and recombined. The results support a conclusion that major histocompatibility restriction of the interaction between T lymphocytes and APC is due to the association between processed antigen and an APC element containing I-region products.

Molecular events in the processing of avidin by antigen-presenting cells (APC). II. Identical processing by APC of H-2 high- and low-responder mouse strains

The differences between the immune response (Ir) phenotypes of H-2 gene-controlled high- and low-responder mice have been attributed to events occurring at the interaction between antigen-presenting cells (APC) and lymphocytes. To investigate this interaction we undertook a study of molecular events in the processing of avidin, a molecule whose uniquely strong affinity for binding to biotin renders it traceable at very low concentrations, and a molecule to which the T-lymphocyte immune response is controlled by Ir genes. In this paper we describe the generation of processed avidin by APC and characterize it biochemically and immunologically. We found that APC of H-2 genetically high- and low-responder mice were indistinguishable in their capacity to generate immunogenic processed avidin (PA). Immunogenic PA differed from native avidin in size and carbohydrate moieties, but preserved its capacity to bind biotin, and was 1000-fold more efficient than NA as an immunogen for primed T lymphocytes. Primed T lymphocytes appeared to recognize PA that was conformationally intact. Highly immunogenic PA was not H-2 restricted. Thus, differences in the Ir phenotype of the response to avidin could not be attributed to determinant selection by APC.

Molecular events in the processing of avidin by antigen-presenting cells (APC). I. The immune response of T lymphocytes to avidin is regulated by H-2-linked Ir genes

The immune response of T lymphocytes to avidin was measured by proliferative assays, antibody production and delayed-type hypersensitivity. Mice of H-2k haplotypes were found to be low responders, whereas mice of other haplotypes, and particularly of H-2s, were high responders. Ir genes controlling this response were mapped to the I subregion of H-2. Helper T cells were found to be responsible for the Ir phenotype of antibody production. These results indicate the feasibility of using the avidin-biotin complex as a tool for studying molecular mechanisms by which antigens under Ir gene control are processed and presented to T lymphocytes.

Abnofmalities in brain myelin or rabbits with experimental autoimmune multiple sclerosis-like disease induced by immunization to gangliosides

An experimental autoimmune multiple sclerosis-like disease (EAMSD) was induced in rabbits by immunizing them with bovine brain gangliosides. Forebrain myelin was isolated and fractionated on a discontinuous sucrose gradient into light myelin (LM, buoyant density less than or equal to 0.625 M), and heavy myelin (HM, buoyant density greater than 0.625 M). No abnormalities in either protein or lipid composition of EAMSD myelin fractions were observed. However, the EAMSD tissue yielded 31% less light and 39% more heavy myelin compared to the control brains. Thus, the HL/LM ratio was two-fold greater in experimental than in control myelin. This pathological pattern is similar to that which has been observed in myelin obtained from the brains of multiple sclerosis patients and from the optic nerves of rabbits with experimentally-induced demyelination.

Genetic control of experimental autoimmune encephalomyelitis at the level of cytotoxic lymphocytes in guinea pigs

To analyze immunologic mechanisms involved in experimental autoimmune encephalomyelitis (EAE), a system for studying the cytotoxic reaction of guinea pig lymphocytes against syngeneic macrophages pulsed with myelin basic protein (BP) was developed. It was found that both EAE-susceptible strain 13 and EAE-resistant strain 2 animals developed cytotoxicity directed against whole BP. However, only strain 13 guinea pigs developed such cells in response to immunization with the encephalitogenic nonapeptide determinant of BP. Strain 2 macrophages appeared able to present the nonapeptide determinant to strain 13 lymphocytes. Anti-BP cytotoxic lymphocytes were found to be recruited by anti-BP initiator lymphocytes.

Experimental autoimmune encephalomyelitis (EAE) mediated by T cell lines: process of selection of lines and characterization of the cells

This paper describes alternative ways of deriving lines of rat lymphocytes capable of mediating EAE. The cells were demonstrated to bear markers specific for T lymphocytes and to be negative for surface Ig, and for Fc and complement receptors. The line cells were found to proliferate in vitro specifically in response to myelin basic protein (BP) associated with accessory cells syngeneic at the major histocompatibility complex (MHC). This accessory cell function could not be provided by purified populations of adherent cells from spleen, peritoneal exudates, or bone marrow cultures alone.

Experimental autoimmune encephalomyelitis (EAE) mediated by T cell lines: process of selection of lines and characterization of the cells

This paper describes alternative ways of deriving lines of rat lymphocytes capable of mediating EAE. The cells were demonstrated to bear markers specific for T lymphocytes and to be negative for surface Ig, and for Fc and complement receptors. The line cells were found to proliferate in vitro specifically in response to myelin basic protein (BP) associated with accessory cells syngeneic at the major histocompatibility complex (MHC). This accessory cell function could not be provided by purified populations of adherent cells from spleen, peritoneal exudates, or bone marrow cultures alone.

Autoantibodies to insulin receptor spontaneously develop as anti-idiotypes in mice immunized with insulin

Mice immunized with insulin developed antibodies to both insulin and the insulin receptor. The antibodies to insulin receptor displaced labeled insulin from insulin receptors and mimicked the actions of insulin in stimulating the oxidation of glucose and its incorporation into lipids, and in inhibiting lipolysis. The antibodies to insulin receptor could be blocked by or bound to the antibodies to insulin, and therefore were identified as anti-idiotypes. Thus, immunization against a hormone may activate spontaneously an idiotype-anti-idiotype network resulting in antibodies to the hormone receptor.

Vaccination against autoimmune encephalomyelitis (EAE): attenuated autoimmune T lymphocytes confer resistance to induction of active EAE but not to EAE mediated by the intact T lymphocyte line

Autoimmune encephalomyelitis (EAE) can be induced in genetically susceptible rats by active immunization against myelin basic protein (BP) or by passive transfer or anti-BP lymphocytes. We have developed in vitro lines of T lymphocytes reactive only against BP that produce EAE upon i.v. inoculation of syngeneic rats. The object of the present study was to learn whether attenuated anti-BP line cells could be used to vaccinate rats against passive as well as active EAE. We inoculated rats i.v. with anti-BP line cells that were attenuated by irradiation or treatment by mitomycin C. A single inoculation was sufficient to protect about 70% of rats from subsequent EAE induced actively. However, even repeated vaccination could not protect against EAE mediated by passive transfer of anti-BP line cells. Thus, attenuated cells of EAE effector lines cannot vaccinate the autoreactive effects of preformed effector T lymphocytes.