<i>In vitro</i> functional activity of T lymphocytes under the conditions of ‘cell neighborhood’ of proliferating and apoptotic cells in healthy people and patients with rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory, autoimmune disease, the development of which is associated with impaired mechanisms of cell number control, proliferation balance, and apoptosis. The aim of our study was to perform a comprehensive analysis of cellular and humoral effects exerted by “apoptotic” T lymphocyte culture upon “proliferating” cells, taking into account the parameters of “primary” and “secondary” apoptosis induction, activation and proliferation markers, viable cell contents, role of cortisol, caspase and cytokines during cultivation under the “cell neighborhood” conditions in healthy subjects and patients with RA. The results of the analysis, with respect to previous data, revealed both similar and different functions of the T cell systems generated under “cell-neighborhood” conditions in healthy individuals and RA patients. Both groups under study were characterized by secondary induction of apoptosis, which refers to non-autonomous effects, along with appearance of activated T lymphocytes at significant amounts, increase of IL-6 and IL-4 levels, as well as low levels of IFNγ and caspase 8, decrease potential of receptor and mitochondrial apoptosis. No differences in apoptosis level were found between donor and patient groups. At the same time, the initially high level of TNFα in healthy subjects decreased during the induction of apoptosis, along with moderate increase of IL-6. The levels of intracellular p53 and Bcl-2 molecules did not change, and many positive correlations remained between the studied factors in all variants of mixed and “apoptotic” cultures, thus suggesting maintenance of functional T cell balance under the unfavorable conditions in donors. The RA patients were characterized by increased number of live cells in “apoptotic” cultures, a significant increase in the number of Ki-67+ T lymphocytes, being indicative for proliferative processes under conditions of apoptosis, like as absence of TNFα response to apoptosis induction. Lack of relations between the studied molecules in “apoptotic” cultures and local cortisol synthesis, as well as presence of correlations between cortisol and the studied molecules in apoptotic cultures, presumed some changes of intercellular interactions and disturbance of homeostasis among T lymphocytes under the conditions of “cellular neighborhood” were also observed in RA patients.

Keywords

• t cells
• apoptosis
• autonomous effects
• non-autonomous effects
• cell neighborhood
• cortisol
• local production
• rheumatoid arthritis