Immune Responses Against Salmonella

Salmonella is recognized as an optional intracellular pathogen. This bacterium can reside within the host’s gastrointestinal tract or encounter phagocytes during its penetration of the mucosal epithelium. To combat Salmonella infections, both cellular and humoral immune responses are essential. Salmonella-specific antibodies produced by B cells can opsonize extracellular bacteria for phagocytosis by phagocytes. Once engulfed, Salmonella spreads systemically within phagocytes and reaches target organs such as the liver and spleen. This bacterium is capable of surviving and replicating within macrophages and dendritic cells (DCs). Professional antigen-presenting cells (APCs) such as macrophages and DCs utilize major histocompatibility complex (MHC) molecules as receptors to present peptides to T cells. When these peptides are presented by MHC molecules, they are displayed on the surface of APCs for recognition by T cell receptors (TCRs). In addition to macrophages and DCs, B cells can also function as APCs. Recognition of the antigen by TCR leads to the activation and proliferation of CD۴+ T cells. These cells, in addition to producing immunoglobulin (Ig) antibodies, also express cytokines that are crucial for the differentiation and function of CD۴+ T cells. Activated CD۴+ T cells, in turn, provide essential stimulation for B cells to undergo class switching of Ig antibodies, as well as for the activation and proliferation of cytotoxic CD۸+ T cells and phagocytic cells such as macrophages. Thus, given that Salmonella requires survival within the host’s phagocytic cells, this aspect provides a framework for a better understanding of adaptive immunity.

کلیدواژه ها:

Salmonella ، Typhoid ، T lymphocytes ، B lymphocytes ، Adaptive Immunity