Role of Citrullinated Fibrinogen Peptides in the Activation of CD4 T Cells from Patients with Rheumatoid Arthritis

This study was conducted to determine whether CD4 T cell responses to citrullinated fibrinogen occur in patients with rheumatoid arthritis (RA), especially in HLA-DR4-positive subjects. Whole peripheral blood mononuclear cells (PBMCs) of RA patients and control subjects were stimulated with citrullinated fibrinogen peptides, and T-cell production of proliferation and proinflammatory cytokines, such as interferon-gamma(IFN-gamma) and interleukin-17A (IL-17A), were measured. In addition, CD4 T cells from RA patients were stimulated with the citrullinated fibrinogen peptide, Fib-alpha R84Cit, identified as a DRB1*0401-restricted T cell epitope in HLA-DR4 transgenic mice, and the degree of T cell activation was examined similarly. No proliferative responses to the citrullinated fibrinogen peptides were observed in whole PBMCs or CD4 T cells from RA patients. Furthermore, no increased production of IFN-gamma or IL-17A was found in whole PBMCs or CD4 T cells stimulated with the citrullinated fibrinogen peptides, although these cells responded to recall antigen, a mixture of tetanus toxoid, purified protein derivative (PPD) from Mycobacterium tuberculosis, and Candida albicans. The results of this study indicate that anti-citrulline immunity in RA patients may be mediated by fibrinogen because there is no evidence of CD4 T cell-mediated immune responses to citrullinated fibrinogen peptides.

Studies on the Cellular Immune Response in Animal Model of Arthritis after the Induction of Oral Tolerance

Oral administration of antigen has long been considered as a promising alternative for the treatment of chronic autoimmune diseases including rheumatoid arthritis (RA), and oral application of type II collagen (CII) has been proven to improve pathogenic symptoms in RA patients without problematic side effects. To further current understandings about the immune suppression mechanisms mediated by orally administered antigens, we examined the changes in IgG subtypes, T-cell proliferative response, and proportion of interleukin (IL)-10 producing Th subsets in a time course study of collagen induced arthritis (CIA) animal models. We found that joint inflammation in CIA mouse peaked at 5 weeks after first immunization with CII, which was significantly subdued in mice pre-treated by repeated oral administration of CII. Orally tolerized mice also showed increase in their serum level of IgG1, while the level of IgG2a was decreased. T-cell proliferation upon CII stimulation was also suppressed in lymph nodes of mice given oral administration of CII compared to non-tolerized controls. When cultured in vitro in the presence of CII, T-cells isolated from orally tolerized mice presented higher proportion of CD4+ IL-10+ subsets compared to non-tolerized controls. Interestingly, such increase in IL-10 producing cells were obvious first in Peyer's patch, then by 5 weeks after immunization, in mesenteric lymph node and spleen instead. This result indicates that a particular subset of T-cells with immune suppressive functions might have migrated from the original contact site with CII to inflamed joints via peripheral blood after 5 weeks post immunization.

The Usefulness of Pleural IFN-gamma Level in Differential Diagnosis of Tuberculous Pleural Effusion and Malignant Pleural Effusion / 결핵

BACKGROUND: It is sometimes difficult to differentiate tuberculous pleural effusion from malignant pleural effusion by clinical symptoms, signs, by routine tests of pleural fluid, and by pathologic studies. And recently, it was discovered that cytokines such as IL-2, IFN-gamma TNF-alpha are elevated in tuberculous pleural fluid, and there have been several attempts to diagnose tuberculous pleural effusion by using these immunological mediators. There are several studies regarding the diagnostic value of IFN-gamma, and there are two studies in Korea. But the diagnostic values of IFN-gamma in these studies were slightly lower than those in other countries. To compare the diagnostic value of IFN-gamma with those of CEA and ADA, and to determine the sensitivity and specificity of IFN-gamma in Korean, we mesured IFN-gamma, CEA level and ADA activity in pleural effusions. METHODS: ADA activity, IFN-gamma level and CEA level as well as cell count, differential count, and biochemical assays such as protein content and lactate dehydrogenase were measured in 40 cases of tuberculous pleuritis and 42 cases of malignant pleural effusion. RESULTS: Tuberculous pleural fluid showed higher levels of IFN-gamma and ADA (832.6+/-357.2 pg/ml and 82.5+/-25.9 U/L, respectively) than those of malignant pleural effusion (2.6+/-8.0 pg/ml and 19.2+/-10.9 U/L, respectively) (p<0.01). Malignant pleural effusions showed higher median value (102.2 ng/ml) than tubercalous pleural effusions (1.8 ng/ml) (p<0.01). The sensitivities of IFN-gamma, ADA, CEA were 0.97, 0.87, 0.67 and the specificities of IFN-gamma, ADA, CEA were 1.0, 0.97, 1.0, respectively. There was no significant correlation between ADA activity and IFN-gamma level. CONCLUSION: This study showed that IFN-gamma test would be a very useful clinical test for differential diagnosis of tuberculous pleuritis and malignant pleural effusion because it is very sensitive and specific, although it is an expensive test.