T cell differentiation by human parvovirus B19 non-structural protein 1 induced apoptotic bodies

New information about the human immune system and its functions is constantly being gathered. The innate and adaptive immunities work in coherence against various pathogens. Dendritic cells (DCs) bridge the gap between the innate and adaptive immune systems by stimulating T and B lymphocytes. Antigen presentation between class II major histocompatibility complex (MHC II) and a T cell receptor, with an additional co-stimulation through receptor-ligand interaction or by a cytokine signal, stimulates CD4+ T cells to differentiate. A variety of differentiated CD4+ T helper (Th) cells are known to participate differently in diverse immune responses such as protection against viruses. For instance, human parvovirus B19 (B19V) infects children and adults alike. The symptoms vary from none to flu-like symptoms to more serious diseases such as erythema infectiosum (fifth disease), arthropathy and hydrops fetalis. Furthermore, B19V has been implicated in autoimmune diseases like rheumatoid arthritis and systemic lupus erythematosus. However, the exact mechanism of pathogenicity is yet unknown. Nonetheless, the nonstructural protein 1 (NS1) is known to cause cell damage and even apoptosis in the host. Hence, examining the capability of NS1 to trigger an immune response was studied. The aim of this study was to investigate DC and T cell interaction after the stimulation with B19 NS1 induced Apoptotic Bodies (ApoBods). The hypothesis was that NS1 induced ApoBods stimulate an immune reaction in vitro, in which the autoimmune related Th1 and Th17 cells are differentiated. A seven-day maturation period for the commercial dendritic cells (MUTZ-3, the cytokine-dependent human cell line) was set up, and the maturation was finalized with a 48 h stimulation period with NS1 induced ApoBods. Afterwards, stimulated MUTZ-3 cells were co-cultured with T cells for 24 h, 72 h and 7 d. Flow cytometry and confocal microscopy were used to examine the extracellular markers on both the mature MUTZ-3 cells and the co-cultured T cells from each of the three time points. CD83 was the extracellular marker for mature DC detection, while six different T cell subtype markers were used for T cell labeling: CD8a, CD4, and CD183 for Th1, CD194 for Th2, CD196 for Th17, and CD25 for T regulatory (Treg) cells. Additionally, the supernatants from the 24 h and 72 h time points were studied for cytokine production. The results of the DC maturation experiment illustrated >10 % maturation of dendritic cells. Moreover, the co-cultured T cells demonstrated differentiation of each T cell subtype examined. The formation of differentiated Th2 cells after 72 h was at a higher quantity than the other CD4+ T cell subtypes (Th1, Th17, and Treg). At day 7, the Th1 and Th17 cells had steadily increased to 2.5 % and 1.5 %, respectively. Although Th2 and Treg cells had first increased at 72 h time point, both had decreased at 7 d. Furthermore, the cytokine analysis exemplified the production of proand antiinflammatory cytokines. However, no signature cytokines for each T cell subtype were discovered. Still, it can be noted that NS1 induced ApoBods stimulated an inflammatory immune reaction, where a variety of T cell subtypes were formed. Moreover, the hypothesis was proven accurate, as Th1 and Th17 cells had differentiated, and the number of cells had increased throughout the experimented time points. Still, further studies on NS1 induced immune reactions are required to identify the exact mechanisms of initiation for B19V –related autoimmunity.