Regulatory T cells (Treg) enriched in FoxP3⁺, glucocorticoid-induced TNF receptor⁺, and cytotoxic T-lymphocyte-associated antigen-4⁺ exert a potential to suppress effector T cells in the periphery. These cells exist in markedly higher proportions within tumor-infiltrating lymphocytes, peripheral blood lymphocytes, and/or regional lymph node lymphocytes of patients with cancer and their frequencies are suggested to be strongly related to tumor progression and inversely correlated with the efficacy of treatment. Tumor-specific Treg cells require ligand-specific activation and cell-to-cell contact to exert their suppressive activity on tumor-specific effector cells (CD8⁺ cytotoxic T lymphocytes and CD4⁺ Th cells), which includes decreased cytotoxity, proliferation, and Th1 cytokine secrection. Depletion or blockade of Treg cells can enhance immune protection from tumor-associated antigens that are expressed as self antigens. Recent studies revealed that lymphoma T cells might adopt a Treg profile as well. Studies assessing the influence of chemotherapy on Treg cells have also been included in this review.

In the present study, we have examined the kinetics and magnitude of expression of the CD28 and CD152 molecules on unstimulated and anti-CD3+rIL-2-stimulated peripheral blood CD4+ and CD8+ T cells in patients with chronic lymphocytic leukaemia (B-CLL) and controls. The mean percentages of both CD3+/CD4+/CD28+ and CD3+/CD8+/CD28+ cells were significantly lower in B-CLL than in controls before culture, decreased rapidly, reaching their lowest levels between 24 and 48 h, and returned to basal levels after 72 h of culture. In controls, the lowest proportions of CD3+/CD4+/CD28+ and CD3+/CD8+/CD28+ cells were found after 24 h and returned to prestimulation levels after 48 h of stimulation. We observed significantly higher proportions of unstimulated CD3+/CD4+/CD152+ and CD3+/CD8+/CD152+ cells in B-CLL patients than in controls. The highest percentages of CD3+/CD4+/CD152+ and CD3+/CD8+/CD152+ cells were observed in controls after 72 h, and in B-CLL patients after 24 h, and remained statistically higher after 48, 72 and 96 h of stimulation. CD152 molecule expression returned to prestimulation levels after 96 h of culture in controls, and after 120 h in B-CLL patients. The abnormal kinetics and levels of CD28 and CD152 expression on T cells in B-CLL may lead to a state of hyporesponsiveness or anergy and could be one of the mechanisms of immune deficiency in this disease.

Summary: Cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4) is an important molecule in the down‐regulation of T‐cell activation. A study was undertaken to evaluate the association of the CTLA‐4 gene polymorphisms −319C/T, +49A/G, (AT)_n, CT60A/G and Jo31G/T with the levels of membrane CTLA‐4 (mCTLA‐4) and cytoplasmic CTLA‐4 (cCTLA‐4) in CD4⁺ T lymphocytes from patients with multiple sclerosis (MS) and with susceptibility to MS, and the course of the disease. It was found that the Jo31GG and CT60GG genotypes were associated with decreased mean fluorescence intensity (MFI) of total CTLA‐4 (mCTLA‐4 + cCTLA‐4) molecules in CD4⁺ T cells from both relapsing‐remitting (RR) and secondary progressive (SP) MS patients compared with others. Consequently, possessing the Jo31G allele and/or the CT60G allele were associated with susceptibility to MS. The percentages of cells expressing mCTLA‐4 and cCTLA‐4 in RR patients were higher in carriers of the alleles non‐predisposing to MS (namely CT60A and Jo31T), but the percentages of corresponding cells were unexpectedly significantly lower in SP patients than in RR patients. Increased risk of paresthesia and pyramidal signs as a first manifestation of disease, and earlier transition to the SP form in those patients, was also noted. It is hypothesized that the decreasing frequencies of cells expressing immunosuppressive mCTLA‐4 and cCTLA‐4 in carriers of alleles non‐predisposing to MS (i.e. CT60A and Jo31T) may lead to inadequate down‐regulation of ongoing T‐cell responses in these patients and, as a consequence, earlier progression of disease from the RR form to the SP form.

Dysregulation in the immune system plays an important role in the pathogenesis of rheumatoid arthritis (RA). The persistent nature of arthritis strengthens the suggestion of immune dysfunction, consisting in predominance of the pro-inflammatory response. It seems that both local and systemic immune abnormalities, including PBMC secreting abnormal levels of pro- and anti-inflammatory cytokines, may be involved in the evolution of the disease. Helper T cells (Th) differentiate towards Th1, Th2, Th17, and Treg cells according to the cytokine microenvironment. Active RA results from the imbalance in distribution of functional pro-inflammatory Th17 and anti-inflammatory Treg cells. Affected Th1 cytokine secretion observed in the course of RA contributes to the increase in IL-17 production and Th17 infiltration in the synovial tissue. Current studies have demonstrated that pro-inflammatory Th1 cytokines may also exert an anti-inflammatory action on the balance between Th17 and Treg cells by promotion of Treg differentiation. In the paper, we also show the influence of TNF-alpha and its inhibitors on the distribution of Th subpopulations in RA patients.