The possible role of class II major histocompatibility complex antigens in self tolerance

Central Nervous System Microglial Cell Activation and Proliferation Follows Direct Interaction with Tissue-Infiltrating T Cell Blasts

Central nervous system (CNS)-resident macrophages (microglia) normally express negligible or low level MHC class II, but this is up-regulated in graft-vs-host disease (GvHD), in which a sparse CNS T cell infiltrate is observed. Relative to microglia from the normal CNS, those from the GvHD-affected CNS exhibited a 5-fold up-regulation of characteristically low CD45, MHC class II expression was increased 10- to 20-fold, and microglial cell recoveries were enhanced substantially. Immunohistologic analysis revealed CD4+αβTCR+CD2+ T cells scattered infrequently throughout the CNS parenchyme, 90% of which were blast cells of donor origin. An unusual clustering of activated microglia expressing strongly enhanced levels of CD11b/c and MHC class II was a feature of the GvHD-affected CNS, and despite the paucity of T lymphocytes present, activated microglial cell clusters were invariably intimately associated with these T cells. Moreover, 70% of T cells in the CNS were associated with single or clustered MHC class II+ microglia, and interacting cells were predominantly deep within the tissue parenchyme. Approximately 3.7% of the microglia that were freshly isolated from the GvHD-affected CNS were cycling, and proliferating cell nuclear Ag-positive microglia were detected in situ. Microglia from GvHD-affected animals sorted to purity by flow cytometry and cultured, extended long complex processes, exhibited spineous processes, and were phagocytic and highly motile. These outcomes are consistent with direct tissue macrophage-T cell interactions in situ that lead to activation, proliferation, and expansion of the responding tissue-resident cell.

Local immune response after intravesical interferon gamma in superficial bladder cancer

OBJECTIVE

To investigate the lymphocyte subpopulations (T4, T8 and macrophages) and major histocompatibility (MHC) II antigens in patients with superficial bladder cancer before and after intravesical instillations of recombinant interferon-gamma (IFN-gamma).

PATIENTS AND METHODS

Four intravesical weekly instillations of either 1.3 mg (20 patients, group A) or 0.7 mg (11 patients, group B) IFN-gamma were administered in 31 evaluable patients (28 men and three women, mean age 68.5 years). The CD4+, CD8+, CD68+ and HLA-DR antigens were detected immunohistochemically in tumours and a marker tumour before and after intravesical instillations.

RESULTS

The median number of T4 lymphocytes increased from 15 per high-power field (HPF) to 27.5 in group A (P = 0.0029) and to 45 in group B (P = 0.0117). Macrophages increased from 6 cells/HPF to 15 cells/HPF in group A (P = 0.0029) and from 2 to 8.75 cells/HPF in group B (P = 0.0117). The T8 lymphocyte subpopulation decreased from 4 to 3 cells/HPF (P = 0.0231) in group A and from 5 to 2 cells/HPF (P = 0.0759) in group B. The median percentage of HLA-DR antigens increased from 1.5% to 18% in general, (P < 0.001), from 2.5% to 15% in group A (P = 0.0064) and from 0% to 20% in group B (P = 0.0077). The induction of HLA-DR antigens was statistically significant in those receiving the lower dose (from 0% before instillation to 20% afterward, P = 0.0277), while it was not with the higher dose (from 0% to 5%, P = 0.068). Irrespective of the dose of IFN used. T4 lymphocytes and macrophages increased significantly after treatment in patients in whom the tumour HLA-DR antigens were either up-regulated or remained stable. The median net increase in T4 cells was 17.5 and 30 cells/HPF for groups A and B, respectively (P = 0.0429).

CONCLUSION

T4 lymphocytes, macrophages and HLA-DR antigens increased after intravesical IFN-gamma in patients with superficial bladder cancer, but T8 lymphocytes decreased. Irrespective of the drug dose used, patients with either upregulated or stable HLA-DR antigens after treatment showed the same pattern of changes in the lymphocyte subpopulations. The two doses generally had the same effect on the immunological variables assessed but the lower dose was more effective in inducing HLA-DR antigens and in increasing the number of T4 lymphocytes in the tumours.

Biological implications of HLA-DR expression in tumours

HLA-DR antigens show restricted tissue distribution in comparison with the more extensive expression of HLA class I molecules. This constitutive expression is genetically controlled by well-defined mechanisms. In addition, DR antigen expression can be induced by a variety of cytokines through different molecular genetic events that convert DR-negative epithelia into positive cells. In this review we analyse the two major pathological situations in which abnormal DR expression occurs: autoimmune diseases and tumour development. We hypothesize that conversion to DR-positivity may produce two opposite effects in both clinical situations: (1) a useful one in tumours associated with a good prognosis; and (2) a harmful one in autoimmune diseases with increased tissue damage.

Intravesical Evans strain BCG therapy: quantitative immunohistochemical analysis of the immune response within the bladder wall

Previous studies have demonstrated that is is the local immune response which is of importance for the anti-tumour activity of BCG therapy. We have investigated this by quantitative immunohistochemical analysis of serial bladder mucosal biopsies taken before, during and after an eight week course of intravesical Evans strain BCG therapy and three monthly thereafter in 16 patients (15 extensive CIS and one extensive G2pTa papillary tumour). This particular group of patients had a 67% complete response rate at six months post-treatment. The main findings on immunohistochemical analysis were the universal induction of MHC Class II antigens by urothelial cells which was statistically significant up to 6 months after completion of therapy, coupled with a T cell dominated cystitis. Increases in CD3+ T cell infiltration of the lamina propria and that of the CD4+ "Helper" subset which predominated were significant up to 3 months post-therapy and these cells showed evidence of increased immunological activation as shown by increased interleukin-2 receptor and MHC Class II antigen expression. There were also significant increases in CD68+ macrophage and the incidence of CD22+ B cell aggregates but CD57+ NK cells were sparse both before and after therapy. The degree of mononuclear cell infiltration for all markers examined (except CD57) was significantly greater in those biopsies in which the urothelial cells expressed MHC Class II antigens than in those that did not. Also the degree of T cell infiltration (CD3, CD4 and CD8) was significantly greater in the eight patients deemed to have had a complete response compared to those seven with a partial response or treatment failure. These results are discussed in terms of possible mechanisms of action for BCG therapy and in particular the role of enhanced antigen presentation by tumour cells.

Radio-immunoassay detection of interferon-gamma in urine after intravesical Evans BCG therapy

Our previous studies suggested that interferon-gamma (IFN gamma) was produced in the local immune response to intravesical BCG. To confirm this we modified a commercially available radio-immunoassay for detection of this lymphokine in urine. The urinary levels of IFN gamma were compared in serial urine samples taken from six patients undergoing treatment with Evans strain BCG and seven patients receiving intravesical mitomycin C/epirubicin. IFN gamma was detected consistently in response to BCG with levels reaching a peak (mean 67.1 U/ml., range 7.9 to 155.9 U/ml.) four to six hours post-instillation whereas after other intravesical agents no IFN gamma was detectable after seven of 13 instillations. After the remaining six instillations lower levels were detected (mean 7.4 U/ml., range 0.6 to 22.4 U/ml.). The difference in peak levels between the two groups was statistically significant (p less than 0.001 Mann Whitney U test). These results are further evidence of specific cellular immune activity in response to intravesical BCG therapy and suggest anti-tumour mechanisms similar to allograft rejection and autoimmunity.

Effects of local bacillus Calmette-Guerin therapy in patients with bladder carcinoma on immunocompetent cells of the bladder wall

The antitumoral effects of intravesical bacillus Calmette-Guerin against recurrent superficial urothelial bladder cancer seem to be linked to immunological effector mechanisms. To characterize further the local cellular response in the bladder wall of patients receiving intravesical bacillus Calmette-Guerin bladder biopsies were examined before and immediately after a 6-week course of bacillus Calmette-Guerin and for up to 1 year at 3-month intervals thereafter. The results showed a marked infiltration after bacillus Calmette-Guerin therapy predominantly of the suburothelial tissue with mononuclear cells, which expressed activation markers and accumulated to follicle-like granulomatous structures. With regard to T lymphocyte subsets the ratio of T helper-to-T suppressor cells in the bladder wall increased from 0.5 to nearly 2. This phenomenon persisted even in biopsies 1 year after initial treatment. In some probes activated mononuclear cells invaded the urothelium, emanating from suburothelial granulomas. It is tempting to assume that these changes within the local immunocompetent cells are related to the therapeutic effect of bacillus Calmette-Guerin against bladder cancer.

HLA-DR expression by high grade superficial bladder cancer treated with BCG

The local immune response to intravesical BCG therapy for widespread carcinoma in situ and superficial bladder tumour was assessed using immunohistochemical methods on serial biopsies obtained during treatment. The main findings were the induction of a strong level of HLA-DR expression by urothelial cells which persisted for several months after completion of therapy. This coincided with a mononuclear cell infiltrate in the bladder wall consisting predominantly of activated helper T lymphocytes. Smaller numbers of macrophages, suppressor cytotoxic T lymphocytes and B lymphocytes were also found. These new findings confirm that the inflammatory response to BCG involves the urothelium in an immunological reaction and suggest that the success of immunotherapy with intravesical BCG may be due to enhanced tumour antigen recognition.

Local immune responses after intravesical BCG treatment for carcinoma in situ

The lymphoid cellular infiltrates in the bladder biopsies from patients with carcinoma in situ before and after BCG intravesical therapy have been determined and characterised. This has been achieved using a panel of monoclonal antibody probes in an indirect immunoperoxidase technique. These studies have revealed the predominance of T-cells of the helper/inducer phenotype (T4+), beta-lymphocytes (B1+) and macrophages (Leu M3+, 3.9+) in bladder biopsies after BCG therapy. HLA.DR antigens were also expressed on the lymphoid cells infiltrate as well as the urothelial cells. These results suggest that the components of an active immune response were present and enhanced in the bladder wall after BCG therapy.