Mechanisms of lymphocyte migration in autoimmune disease

The recruitment of leukocytes to inflamed tissues plays an essential role in combating infection and promoting wound healing. However, in autoimmune diseases such as multiple sclerosis and diabetes, leukocytes enter tissues and contribute to inappropriate inflammatory responses, which cause tissue injury and dysfunction. In diseases of this type, lymphocytes play critical roles in initiating and maintaining these aberrant inflammatory responses. The aim of this review is to examine the mechanisms whereby T-lymphocytes enter tissues in autoimmune diseases and to compare these mechanisms between various organs and diseases. An overview of the mechanisms of leukocyte recruitment and the techniques used to study leukocyte trafficking is provided, focusing on the use of intravital microscopy as a tool to assess the functional microvasculature in vivo. We also discuss the series of tissue homing events which allow na?ve lymphocytes to first enter lymph nodes and undergo activation, then subsequently to home to the peripheral organ where their cognate antigen is present. Finally, we examine mechanisms of leukocyte recruitment in diseases such as multiple sclerosis, autoimmune diabetes, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease and asthma.     

Attenuation of autoimmune disease and lymphocyte accumulation in MRL/lpr mice by treatment with anti-V beta 8 antibodies.

MRL-MP-lpr/lpr mice are afflicted by a severe systemic autoimmune disease that is aggravated by the lpr mutation resulting in the accumulation of phenotypically abnormal lpr cells (CD3+CD4-CD8-) in all lymphoid issues including hyperplastic lymph nodes. Given that products of the T cell receptor V beta 8 gene family are overrepresented among lpr cells, different schedules aimed at selectively decreasing the frequency of lpr cells were designed. First, continuous administration of the monoclonal antibody F23.1 (specific for V beta 8 products) resulted in a significant depletion of V beta 8+ cells and prevented the manifestation of lymph accumulation at the same time as it reduced the serological, clinical, and histopathological signs of autoimmune disease. Along the same line, administration of either F23.1 or two different anti-F23.1 anti-idiotypic antibodies to MRL/Mp-lpr/lpr mothers elicited, in the offspring, the production of antibodies sharing a recurrent idiotype with F23.1 and resulted in long-term amelioration of autoimmunity and lymphadenopathy. Thus, a strategy aimed at specifically reducing the frequency of a subset of lpr cells proved successful in mitigating the autoimmune process.     

Impairment of T lymphocyte functions in mice with motor end-plate disease.

The present paper reports complex immunological anomalies associated with motor end-plate disease (Med) in mice. Motor end-plate disease is a severe neuromuscular disorder which leads to death (around the 25th of life) in the Medj/Medj mutant, while the heterozygotes quickly recover from mild manifestations. Medj/Medj and Medj/ + mice share some of the immunological aberrations: reduced PFC response to SRBC in 14-16 day old mice, with reduced suppressor cell function and precocious maturation of the cytotoxic response to allogeneic cells in 21-23 day old mice. The diminished PFC response is corrected in adult Medj/ + mice but persists in the small group of Medj/Medj which escape death and which were studied between the 6th and 16th week of life. In addition, the thymus and spleen of Medj/Medj mice are greatly reduced in size, a symptom which appears with the onset of the clinical disease. Also, a reduction in the NK activity in the small group of older, surviving mice was noted. T and B lymphocyte proportions and the proliferative responses to T cell mitogens were not impaired in 14-16 day old mice. The role of these abnormalities in the pathogenesis of the disease is not known. Since some of these anomalies are shared by Medj/Medj and Medj/ +, the latter of which present no or mild and transient neurological manifestations, there is no clear link between the immunological and neuromuscular disorders.     

Suppression of autoimmune disease in New Zealand mice associated with infection in malaria. II. NZB mice

The onset of a positive Coombs test was significantly delayed in NZB mice infected with Plasmodium berghei at the age of 1 month. At the age of 12 months, twelve out of fourteen malaria-infected NZB mice had become Coombs positive but their reticulocyte counts and mean spleen weight were significantly lower than those of control NZB mice of the same age.     

Experimental autoimmune thyroiditis: attempt to correlate disease development with lymphocyte subset changes.

An attempt was made to correlate lymphocyte subset abnormalities with the development of experimental autoimmune thyroiditis (EAIT) in thymectomized and irradiated rats of five inbred strains. The peripheral blood subpopulations were analysed using the fluorescence-activated cell sorter (FACS-IV). A significant lymphopenia with a severe decrease in helper T cells was identified in all the treated rats. In addition, a significant loss of suppressor cytotoxic T cells was found in rats of the most susceptible strain (August) and in the majority of affected individual rats of the other strains. The simple, modified protocol which we used revealed differences in strain susceptibility to EAIT, with 66% of August rats having histological evidence of disease, 50% of Lewis, 44% of Agus, 30% of Hooded Lister and 20% of Wistar, at 5 to 8 months after treatment. Levels of antithyroglobulin antibody, estimated by an ELISA assay, correlated well with the histological results. In all groups, three times as many females as males were affected. Our findings support the view that genetic and immunoregulatory factors are involved in the development of EAIT, with loss of both helper and suppressor cells playing an important role.     

T lymphocyte autoimmunity in peripheral nervous system autoimmune disease

Conclusion Autoaggressive T cells specific for the PNS myelin P2 protein play a central role in the initiation of EAN in the Lewis rat, although there is as yet no direct experimental evidence that the T cells can themselves mediate demyelination in vivo. However, the striking similarities in the pathogenesis of EAN and the Guillain-Barré syndrome suggest that T cell mediated EAN provides an excellent model to study the immunological mechanisms of inflammation and demyelination that are relevant to human PNS disease.     

Deficiency of the autologous mixed lymphocyte reaction in patients with autoimmune thyroid disease

The proliferative response of T lymphocytes when cocultured with autologous non-T cells in the absence of any other stimulating substance has been termed the autologous mixed lymphocyte reaction (AMLR). The AMLR has been shown to be impaired in several autoimmune disorders, such as systemic lupus erythematosus, Sj?gren's syndrome, and primary biliary cirrhosis. In this study we report marked deficiency in the AMLR in two autoimmune disorders: Hashimoto's and Graves' diseases. This impaired AMLR, probably related to previously described T cell subset imbalances, provides further evidence of altered interactions between the immunocompetent cellular subsets in patients with these pathological conditions. Additional preliminary observations suggest defective allogeneic mixed lymphocyte reactions as well.     

Increased amplifier T cell activity in autoimmune NZB mice and its possible significance in the expression of autoimmune disease

The expression of amplifier- and helper-T cell activity was examined in NZB/N mice of different ages. Amplifier T cell activity develops in a cyclic manner; it decreases between 16 and 35 wk of age and then increases to maximal levels in mice older than 50 wk of age. The loss of suppressor T cell activity and increased amplifier T cell activity coincide with the development of autoimmune diseases in aging NZB/N mice. Although helper T cell activity is evident in young NZB/N mice, it is absent in old NZB/N mice expressing maximal amplifier T cell activity. This provides additional support for the fact that amplifier and helper functions are mediated by different subpopulations of T cells.     

Preservation of T-lymphocyte activity in autoimmune MRL-lpr mice treated with prostaglandin

MRL-lpr mice display immunoregulatory disturbances which are related to an early massive T-lymphocyte hyperplasia. Features of autoimmunity are rapidly progressive and these animals die from immune complex-mediated glomerulonephritis. Previous studies show that 15 methyl prostaglandin E1 (PGE) treatment in MRL-lpr mice prolongs survival by preventing lymphoproliferation and the subsequent renal disease. The present study indicates that a major activity of this therapy stabilizes several T-cell functions. Both the age-related loss of the autologous mixed-lymphocyte reaction (AMLR) (Ly1+ 2,3- dependent) and the concanavalin A-induced suppressor cell activity (Ly1- 2,3+ dependent) remain intact. It is suggested that PGE preserves these T-cell functions by maintaining a more normal balance of T-cell subsets.     

Increase in peripheral natural killer cell activity in patients with autoimmune thyroid disease.

Changes in the activity and number of natural killer (NK) cells in peripheral blood in patients with autoimmune thyroid disease were examined. NK activity was measured in a 4-hr 51Cr-release assay and the number of NK cells was analyzed with FITC-conjugated monoclonal antibodies by use of an automated flow cytometer. NK activity in patients with untreated Graves' disease (n = 25, 39.7 +/- 13.5%, P less than 0.05) and Hashimoto's thyroiditis (n = 18, 41.0 +/- 14.2%, P less than 0.05) was high compared to the activity in non-pregnant controls (n = 61, 32.6 +/- 15.0%). NK activity in patients with postpartum Graves' thyrotoxicosis (n = 11, 48.6 +/- 18.9%) was markedly increased compared to the activity in non-pregnant controls (P less than 0.01) and in postpartum controls (n = 29, 33.8 +/- 15.2%, P less than 0.05), although the mean ages of each group did not differ significantly. Moreover, NK activities in the thyrotoxic state were significantly higher than those in the euthyroid state in the same patients with postpartum Graves' thyrotoxicosis or with postpartum destructive thyrotoxicosis. The number of CD16 positive cells increased in patients with postpartum Graves' thyrotoxicosis. However the number of CD16 and CD57 positive cells were normal in all other groups of patients. These results indicate that an increase of NK activity is associated with exacerbation of autoimmune thyroid disease both in Hashimoto's thyroiditis and in Graves' disease and suggest that NK cells might have an important role for the control of disease activity in autoimmune thyroid disease.     

Systemic autoimmune disease as a consequence of defective lymphocyte death

A major group of systemic autoimmune diseases is associated with abnormal lymphoproliferation, as a result of defects in the termination of lymphocyte activation and growth. Recent progress has been made in understanding the causes and consequences of these abnormalities. At the molecular level, the defects in CD95 and its ligand are only the most obvious reasons for the breakdown of ‘clonal contraction’ which in fact requires the participation of multiple gene products, including the IL-2—IL-2-receptor system, to set up a functional apoptotic machinery.     

MyD88-dependent autoimmune disease in Lyn-deficient mice

Recent evidence suggests that systemic autoimmune disease depends on signals from TLR ligands, but little is known about how TLR-dependent pathways lead to the loss of self tolerance in vivo. To address this, we have examined the role of TLR signaling in Lyn-deficient mice, which develop an autoimmune disease similar to SLE. We found that absence of the TLR signaling adaptor molecule MyD88 suppresses plasma cell differentiation of switched and unswitched B cells, and prevents the generation of antinuclear IgG antibodies and glomerulonephritis. In mixed chimeras the increased IgM and IgG antibody secretion in Lyn-deficient mice is at least partially due to B cell-independent effects of Lyn. We now show that MyD88 deficiency blocks the expansion and activation of DC in which Lyn is also normally expressed, and prevents the hypersecretion of proinflammatory cytokines IL-6 and IL-12 by Lyn-deficient DC. These findings further highlight the important role of TLR-dependent signals in both lymphocyte activation and autoimmune pathogenesis.     

Thyroid function in mice with experimental autoimmune thyroiditis.

Mice of strains high and low responders to thyroglobulin were immunized with mouse thyroglobulin emulsified in Freund's complete adjuvant. Groups of mice were killed at weekly intervals and the serum thyroxine concentration was measured with a solid-phase RIA while the titre of thyroglobulin antibodies was determined by passive haemagglutination and the magnitude of thyroid infiltration with mononuclear cells was scored. In other groups of mice, similarly immunized, radioactive iodine uptake was measured at various times after immunization. In almost all mice the lowest level of thyroxine and the lowest radioiodine uptake were observed 2 weeks after immunization. There was no clear relationship between the thyroid function and the titre of thyroglobulin antibodies or the extent of the cellular infiltrates in the thyroid.     

Modification of helper and suppressor/cytotoxic lymphocyte subsets in mice with motor end-plate disease.

Motor end-plate disease (Med) in mice is associated with complex immunological abnormalities which are shared by the heterozygous +/MedJ mice, which exhibit no or mild clinical manifestations, and by MedJ/MedJ mice which die from this neuromuscular disorder. In the present paper we extend our immunological data with the study of splenic lymphocyte subsets with Lyt monoclonal antibodies. Both MedJ/MedJ and +/MedJ 14-18 day old mice have high Lyt1+/Lyt2+ ratios, with higher Lyt1+ and reduced Lyt2+ lymphocyte pools as compared to normal mice. This correlates with the low suppressive function previously described, but is unexpected in view of the low helper function as measured by the response to SRBC immunization. Adult +/MedJ mice recovered normal T lymphocyte subset levels, while the small group of MedJ/MedJ mice that escapes death but continues to suffer from the neuromuscular illness maintains high Lyt1+/Lyt2+ ratios.     

Loss of T cell microRNA provides systemic protection against autoimmune pathology in mice

With an increasing number of studies demonstrating alterations in T cell microRNA expression during autoimmune disease, modulation of the T cell microRNA network is considered a potential therapeutic strategy. Due to the complex and often opposing interactions of individual microRNA, prioritization of therapeutic targets first requires dissecting the dominant effects of the T cell microRNA network. Initial results utilizing a unidirectional screen suggested that the tolerogenic functions were dominant, with spontaneous colitis resulting from T cell-specific excision of Dicer. Here we performed a bidirectional screen for microRNA function by removing Dicer from the T cells of both wildtype mice and Transforming Growth Factor β (TGFβ) receptor-deficient mice. This allowed the impact of microRNA loss on T cell activation, effector T cell differentiation and autoimmune pathology to be systematically assessed. This bidirectional screen revealed a dominant immunogenic function for T cell microRNA, with potent suppression of T cell activation, IFNγ production and autoimmune pathology in all targeted organs except the colon, where Dicer-dependent microRNA demonstrated a dominant tolerogenic function. These results reverse the original conclusions of microRNA function in T cells by revealing a systemic pro-autoimmune function.     

Interferon treatment of NZB mice: accelerated progression of autoimmune disease.

The effect of long-term administration of interferon in New Zealand Black and New Zealand Black/New Zealand White F1 hybrid mice was studied. Treatment with moderate doses of interferon (10(4) units, five times weekly for 8 weeks) did not depress murine leukemia virus gp69/71 levels in serum and spleen, nor p30 levels in the spleen. Interferon given at 10(5.1) units (three times weekly for 37 weeks) caused an increased incidence of anti-erythrocyte antibodies in New Zealand Black mice. Finally, the hybrid mice given interferon at 10(6.0) units (three times weekly for 33 weeks) had increased renal immune complex deposits and increased incidences of proteinuria and anemia.