T cell antigen receptor usage, phenotype and cytokine production in human diseases

Abstract

T lymphocytes are of critical importance for initiating and controlling immune responses, as the T cell receptor (TCR) for antigen allows a highly specific antigen recognition. Determination of TCR usage and characterization of T cell subsets in different diseases helps us understand the underlying immunopathogenic mechanisms, and may also lead to the development of new therapeutic approaches.

TCR usage was analyzed at the protein level by anti-TCR Va and V[beta] antibodies and flow cytometry. Vp-specific PCR amplification was followed by CDR3 fragment length analysis, cloning and sequencing or determination of J[beta] gene segment usage. Functional aspects were investigated via antibody staining for cell surface markers or intracellular cytokines.

In allergic alveolitis most patients had lung-restricted CD8+ expansions of T cells using particular V[alpha] or V[beta] segments. These expansions, some of which were dramatic, normalized with clinical improvement. Similarly, patients with allergic asthma developed CD8+ T cell expansions in their lungs after allergen inhalation provocation. The correlation with antigen exposure implicates the expanded I cells in the pathogeneses of these diseases.

In B-cell malignancies the immunoglobulin idiotype may serve as an autoantigen, being recognized by T cells that may have the capacity to control the myeloma tumour clone. Patients with multiple myeloma had more CD8+ T cell expansions, all of which were highly clonal, compared to age-matched controls. Interestingly, expansions were particularly common in patients with a low tumour burden. In Wegener's granulomatosis, a systemic vasculitis of unknown aetiology, very large T cell expansions were previously demonstrated in the CD4+ subset. We determined a high degree of clonality of all the expansions studied. Of utmost interest was the finding of a common, dominating TCR CDR3-motif that was found in CD4+ V[beta]8+ T cell expansions of several unrelated patients sharing the HLA DRB1*0401 allele, but not in age- and HLA-matched controls. This finding therefore suggests the existence of a specific vasculitis-associated antigen.

A phenotypic analysis of T cell subsets in lung and blood of pulmonary sarcoidosis patients was undertaken, focusing on activation markers, adhesion molecules, and costimulatory molecules. There was substancial activation of CD4+ as well as of CD8+ lung T cells, and in the lung increased numbers of CD26+ CD28-CD57+ cells, indicating clonally expanded T helper 1 cells. Significantly more cells capable of producing IFN[gamma] and TNF[alpha], and fewer cells producing IL-4, were detected in both CD4+ and CD8+ lung T cell subsets compared to peripheral blood. Thus both subsets may contribute to the inflammatory process in the lung. The tendency to a relatively less pronounced Th1 response in HLA-DR17+ patients may be related to the very good prognosis of this patient group.

These studies directs the attention to the potentially very important role for CD8+ T cells in several inflammatory pulmonary disorders.