Role and Interrelationship Between Myeloid-Derived Suppressor Cells and CD4+ T Cells in Different Types of Infections: A Review.

Myeloid-Derived Suppressor Cells (MDSCs), also known as 'Natural Suppressor Cells (NSCs)', 'Immature Myeloid Cells, (IMCs), or 'Myeloid Suppressor Cells' (MSCs), are renowned for suppressing the immune functioning of T lymphocytes. Depending on the structural similarity with neutrophils and monocytes, MDSCs can be classified as polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs). On the other hand, T cells, generally subdivided into CD4⁺ and CD8⁺ groups based on the surface glycoprotein, are crucial for generating an adaptive immune response. During the event of an infection, MDSCs and T cells, along with other immune regulatory cells, interplay and generate a robust host immune response against the invading pathogens. In this review, we have highlighted the role of MDSCs and different subsets of CD4⁺ T cells, such as Th1, Th2, Th17, Th9, Th22, T_reg, T_fh, and Tr1 with and various transcription factors associated with them, in different well known bacterial, viral, parasitic and fungal diseases. Changes in the MDSC population were found to be associated with either promotion or suppression of T cell subsets in different infections. The relative frequency and absolute numbers of MDSCs in the peripheral blood, therefore, may serve as an important marker useful in future immunotherapeutics. [ABSTRACT FROM AUTHOR]