The cellular basis for the Ia restriction in murine experimental autoimmune thyroiditis

Autoantibody responses and pathology regulated by B7-1 and B7-2 costimulation in MRL/lpr lupus

The activation of T lymphocytes requires both Ag-mediated signaling through the TCR as well as costimulatory signals transmitted through B7-1 and/or B7-2 with CD28. The interference of B7-mediated costimulatory signals has been proposed as one immunotherapeutic intervention for the prevention autoimmune disease. This study has examined autoantibody responses and autoimmune pathology in a murine model of human systemic lupus erythematosus (SLE), the MRL-lpr/lpr mouse, genetically deficient in B7-1 or B7-2, or in mice treated with B7-1/B7-2 blocking Abs. In contrast to other studies of murine models of SLE, MRL-lpr/lpr mice treated with B7 blocking Abs exhibit strong anti-small nuclear ribonucleoprotein (snRNP) and anti-DNA autoantibody responses with some changes in isotype switching as compared with untreated animals. All MRL-lpr/lpr mice deficient in B7-1 or B7-2 produce anti-snRNP and anti-DNA titers with isotypes virtually identical with wild-type animals. However, the absence of B7-2 costimulation did interfere with the spontaneous activation and the accumulation of memory CD4+ or CD8+ T lymphocytes characteristic of wild-type MRL-lpr/lpr mice. IgG and C3 complement deposition was less pronounced in the kidneys of B7-2 deficient MRL-lpr/lpr mice, reflecting their lessor degree of glomerulonephritis. By comparison, B7-1-deficient MRL-lpr/lpr mice had more severe IgG and C3 deposits in glomeruli.

B7.2 Has Opposing Roles During the Activation Versus Effector Stages of Experimental Autoimmune Thyroiditis

APCs provide costimulatory and down-regulatory signals to Ag-activated T cells through interactions between B7.1 and B7.2 on APCs with either CD28 or CTL Ag-4 expressed on T cells. Recipients of mouse thyroglobulin (MTg)-primed spleen cells activated in the presence of anti-B7.2 had decreased experimental autoimmune thyroiditis (EAT) severity compared with recipients of cells cultured with control rat Ig or anti-B7.1. Blocking B7.2 during in vivo priming also suppressed the ability of MTg-primed spleen cells to transfer EAT, implicating a role for B7.2 for priming and in vitro activation of EAT effector cells. In contrast, administration of anti-B7.2 or anti-B7.2 Fab to recipients of MTg-activated spleen cells increased the severity of EAT compared with recipients receiving control Ig. Thyroids from anti-B7.2-treated recipients had increased expression of IL-4 mRNA compared with thyroids from rat Ig-treated controls. Both B7.1 and B7.2 molecules were expressed in the thyroids of mice with EAT, although B7.2 was more prevalent than B7.1. Administration of both anti-B7.1 and anti-B7.2 to recipient mice suppressed the development of EAT, while anti-B7.1 treatment alone had no effect on EAT severity. The suppression of EAT was not observed when anti-B7.1 and anti-B7.2 treatment was delayed until 7 days after cell transfer, suggesting a requirement for B7 in the initiation of EAT in recipient mice. These results suggest that costimulation is required during the effector phase of EAT and that B7.2 may have opposing roles in the activation versus effector stages of autoreactive T cells.

Restricted heterogeneity of T cell receptor transcripts in rheumatoid synovium

RA is characterized by massive proliferation of synovial tissue, accompanying infiltration of the tissue with CD4+ T lymphocytes, and a genetic linkage to the MHC antigen HLA-DR4. Since T cells are restricted by class II MHC molecules such as DR4, this suggests a direct role for these CD4+ cells in pathogenesis. To investigate T cell receptor (TCR) usage in RA, we used oligonucleotide primers specific for each of the major alpha and beta TCR subfamilies to amplify cDNA derived from whole synovium or synovial tissue T cell lines in a family-specific manner. Detection of amplified DNA was facilitated by utilizing oligonucleotide probes derived from the constant regions of the TCRs. The TCR repertoire present in the synovial T cell lines was quite heterogeneous, with an average of 15 alpha chains and 15.8 beta chains detected. When synovial tissue was analyzed, the predominant TCR subfamilies detected tended to be more restricted, with an average of 4.6 alpha chains and 8.6 beta chains detected. This compared with an average of six alpha chains and 12 beta chains in nonrheumatoid synovial samples. The average percentage of synovia positive per TCR beta family was significantly lower for RA versus non-RA specimens (46.1 vs 65.6%, P = 0.034). These findings indicate that while a polyclonal population of T cells is present in RA synovium, the predominant patterns of TCR transcript expression may be somewhat more restricted, suggesting that TCR-based therapy of RA is possible.

CD5-negative cell mediated experimental hypersensitivity pneumonitis

Experimental hypersensitivity pneumonitis (EHP) can be transferred to Strain 2 guinea pigs by peripheral lymph node (PLN) cells cultured in vitro with antigen. The phenotype of the active cells has not been delineated. In addition, it is not known if cultured lung-associated lymph node (LALN) cells can transfer EHP. PLN and LALN cells from donor animals were cultured with a soluble extract of Micropolyspora faeni (10 micrograms/ml), and blast cells were isolated by centrifugation over Percoll gradients. Cultured PLN cells were passed through nylon wool columns, and the adherent and nonadherent fractions were tested for their ability to transfer EHP. PLN blast cell populations were depleted of CD5+ cells by treatment with monoclonal anti CD5 antibody (8BE6) and complement. Syngeneic recipients received media or LALN or PLN blast cells treated with antibody plus complement, media, or complement intravenously. Recipients were challenged intratracheally with M. faeni 48 h after the cell transfer, and they were killed 4 days later. The nonadherent PLN cell population was enriched for CD5+ (T) cells and depleted of surface immunoglobulin-positive (SIg+) cells. Treatment of the PLN blast cell population with 8BE6 and complement decreased CD5+ cells from 25 to 4% and increased SIg+ cells from 62 to 80%. All animals were maintained in HEPA-filtered air. Randomly selected microscopic fields of the lung (250/animal) were judged to be normal or abnormal without knowledge of treatment. There was a low level of pulmonary response to an intratracheal challenge of M. faeni in media recipients. There was a substantial increase (p less than 0.01) of the extent of pulmonary abnormalities in the animals receiving cultured PLN cells.(ABSTRACT TRUNCATED AT 250 WORDS)

In situ analysis of T cell subset composition in experimental autoimmune thyroiditis after adoptive transfer of activated spleen cells

T cells from genetically susceptible mice developing experimental autoimmune thyroiditis (EAT) proliferate in response to restimulation with mouse thyroglobulin (MTg) in vitro. The in vitro-activated cells adoptively transfer EAT as well as differentiate into cells cytotoxic for syngeneic thyroid monolayers. To examine the kinetics of T cell subset infiltration and distribution in situ after adoptive transfer, we applied the avidin-biotin-peroxidase labeling technique to thyroid sections, utilizing rat monoclonal antibodies followed by a biotinylated rabbit anti-rat antibody. Female CBA donor mice were immunized with MTg and lipopolysaccharide. Their spleen cells were obtained 7 days later, cultured with MTg, and transferred into recipient mice. The thyroids were removed on Days 7, 10, and 14 after transfer and serially sectioned. The early phase of transferred EAT showed a higher percentage of L3T4+ cells compared to Lyt-2+ cells, yielding a ratio of 2.3 and total T cells of about 35%. By Day 10, both T cell subsets had increased to a total of about 56%. However, the relative increase was greater in the Lyt-2+ subset; the nearly doubled percentage was statistically significant, resulting in a downward shift in the subset ratio to 1.7. Little change in the in situ distribution was seen on Day 14. The percentages of F4/80+ (macrophage) population in lesions examined on Days 10 and 14 were fairly constant and B cell involvement was minimal. These findings illustrate the pathogenic role of both T cell subsets in adoptively transferred EAT and the time-dependent changes in their relative proportions leading to thyroid gland destruction.

Effects of anti-I-A and anti-I-E monoclonal antibodies on the induction and expression of experimental autoimmune thyroiditis in mice

Susceptibility to experimental autoimmune thyroiditis (EAT) in mice is linked to the I-A subregion of the major histocompatibility complex (MHC). The present study was undertaken to assess the effectiveness of anti-I-Ak monoclonal antibody (MAb) 10-2.16 in preventing or arresting the development of EAT. Spleen cells from CBA/J or (CBA/J x Balb/c) F1 mice given 10-2.16 prior to sensitization with mouse thyroglobulin (MTg) and adjuvant could not transfer EAT to normal recipients, and cells from these mice did not proliferate in vitro to MTg. Donor CBA/J mice given 10-2.16 before immunization and recipients of cells from such mice produced little MTg-specific IgG1 or IgG2b antibody but did produce nearly as much IgG2a as controls. The effects of in vivo treatment with 10-2.16 appear to be due to elimination of Ia + cells rather than to modulation of Ia or induction of suppressor T cells. When 10-2.16 was added to in vitro cultures it also prevented the proliferation and activation of sensitized CBA/J or F1 effector cell precursors. Other mAb specific for MHC class II gene products, but not associated with disease susceptibility, expressed by CBA/J (I-Ek) or F1 (I-Ad) mice (14-4-4S or MK-D6 respectively), also prevented in vivo sensitization, but did not block in vitro activation. Anti-I-Ak was also effective in preventing EAT if multiple injections of mAb were given to recipients of sensitized EAT effector cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Depletion of L3T4+ and Lyt-2+ cells by rat monoclonal antibodies alters the development of adoptively transferred experimental autoimmune thyroiditis

To delineate the contribution of L3T4+ and Lyt-2+ cells in the pathogenesis of experimental autoimmune thyroiditis (EAT), synergistic pairs of monoclonal antibodies (mAb) to the T cell subsets were used in conjunction with the adoptive transfer of mouse thyroglobulin (MTg)-activated cells from immunized mice. Initial experiments verified the important role of L3T4+ cells in the transfer of EAT. Subsequent experiments pointed to the relative contribution of both L3T4+ and Lyt-2+ cells, depending on the stage and extent of disease development. Treatment during disease with L3T4, but not Lyt-2, mAb alone significantly reduced thyroiditis. However, in situ analysis of the cellular infiltrate in thyroid sections revealed that, after treatment with mAb, the appropriate subset was eliminated without altering the amount of the other subset in the remaining lesion. In addition, treatment during severe thyroiditis following the transfer of MTg-activated lymph node cells showed that Lyt-2 mAb alone also reduced thyroid infiltration. When the recipients were pretreated with either pair of mAb before transfer, disease development was only moderately affected. We conclude that (i) donor L3T4+ cells are the primary cells responsible for the initial transfer and development of thyroiditis; and (ii) previous in vitro cytotoxicity data, plus current monoclonal antibody treatment of disease and in situ analysis, further implicate a role for Lyt-2+ cells in EAT pathogenesis.

Induction of experimental autoimmune thyroiditis in B cell-depleted mice

The effect of B cell depletion on the induction and severity of murine experimental autoimmune thyroiditis was investigated. Thirteen CBA mice were given repeated intraperitoneal doses of 700 micrograms purified rabbit anti-mouse Ig antibody from 24 hours to 8 weeks after birth. Controls were given normal rabbit IgG (14 mice) or were left uninjected (10 mice). At six weeks all mice received two doses of 70 micrograms murine thyroid extract in complete Freund's adjuvant. Only 2/13 of the anti-Ig treated mice were fully B cell-deficient as determined by serum IgM, spleen cell immunofluorescence and responsiveness to LPS; however, the levels of anti-thyroglobulin autoantibodies were very low in 7/13 mice. The results demonstrate that thyroiditis can be actively induced in the absence of B cells and autoantibodies but that B cells may play a role in increasing disease severity.

Prevention and reversal of experimental autoimmune thyroiditis (EAT) in mice by administration of anti-L3T4 monoclonal antibody at different stages of disease development

Experimental autoimmune thyroiditis (EAT) can be induced in CBA/J mice following the transfer of spleen cells from mouse thyroglobulin (MTg)-sensitized donors that have been activated in vitro with MTg. Since L3T4+ T cells are required to transfer EAT in this model, the present study was undertaken to assess the effectiveness of the anti-L3T4 monoclonal antibody (mAb) GK1.5 in preventing or arresting the development of EAT. Spleen cells from mice given mAb GK1.5 prior to sensitization with MTg and adjuvant could not transfer EAT to normal recipients and cells from these mice did not proliferate in vitro to MTg. Donor mice given GK1.5 before immunization did not develop anti-MTg autoantibody and recipients of cells from such mice also produced little anti-MTg. GK1.5 could also prevent the proliferation and activation of sensitized effector cell precursors when added to in vitro cultures. When a single injection of mAb GK1.5 was given to recipients of in vitro-activated spleen cells, EAT was reduced whether the mAb was given prior to cell transfer or as late as 19 days after cell transfer. Whereas the incidence and severity of EAT was consistently reduced by injecting recipient mice with GK1.5, the same mice generally had no reduction in anti-MTg autoantibody. Since EAT is consistently induced in control recipients by 14-19 days after cell transfer, the ability of mAb GK1.5 to inhibit EAT when injected 14 or 19 days after cell transfer indicates that a single injection of the mAb GK1.5 can cause reversal of the histopathologic lesions of EAT in mice. These studies further establish the important role of L3T4+ T cells in the pathogenesis of EAT in mice and also suggest that therapy with an appropriate mAb may be an effective treatment for certain autoimmune diseases even when the therapy is initiated late in the course of the disease.