African swine fever virus (ASFV), the causative agent of one of the most important viral diseases of domestic pigs for which no vaccine is available, causes immune system disorders in infected animals. In this study, the serum levels of proinflammatory cytokines, as well as the histological and cellular constitution of lymphoid organs of pigs infected with ASFV genotype II were investigated. The results showed a high degree of lymphocyte depletion in the lymphoid organs, particularly in the spleen and lymph nodes, where ASFV infection led to a twofold decrease in the number of lymphocytes on the final day of infection. Additionally, ASFV-infected pigs had atypical forms of lymphocytes found in all lymphoid organs. In contrast to lymphocytes, the number of immature immune cells, particularly myelocytes, increased dramatically and reached a maximum on day 7 postinfection. The serum levels of TNF-α, IL-1β, IL-6, and IL-8 were evaluated. Proinflammatory cytokines showed increased levels after ASFV infection, with peak values at 7 days postinfection, and this highlights their role in the pathogenesis of ASFV. In conclusion, this study showed that ASFV genotype II, like other highly virulent strains, causes severe pathological changes in the immune system of pigs.

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The primary culture bone marrow (PCBM) cells are often used in different cytological investigations. Here we study the behavior of porcine unstimulated PCBM cells during the cultivation. DNA cytophotometry analyses revealed that immature white blood cells (WBC) such as lymphoblasts, monoblasts and myeloid cells during cultivation process reduced the DNA content in the nuclei. This resulted in displacement of the DNA histogram to the left and increased the content of diploid nuclei. This is a result of cells unblocking which are in G2 cell cycle phase. We also observed diploid pathological cells with accessory or fragmentized nuclei. However, the data with erythroid cells (EC) somehow demonstrate the opposite tendency. During the late stage of cultivation, the number of immature EC with the tetraploid DNA is increased.

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