Immune Cells

Understanding the effect of microbe-specific regulatory immune cells called T cells (Tregs) on anti-pathogen immunity in the presence of these cells is significant as it can help us understand more about host immunity against infections. A new study aims to identify microbe-specific Tregs in humans in order to determine T cell specificity, by using peptide-MHC tetramers to isolate cells from adult peripheral blood. The findings highlight the importance of antigen specificity as antigen exposure can have a significant effect on the impact of anti-pathogen immunity.

 

The adaptive immune system is where the body adapts to foreign invaders. Within the immune system in the thymus areT cells, which are types of white blood cells that play a critical role in cell-mediated immunity. These types of cells, which have the α/β T-cell receptor (TCR), are crucial for protection against infectious diseases. These T cells are able to express a large range of TCRs, in order to recognize the extensive number of pathogens that encounter the body, as well as remain resistant to the self in order to clear pathogens.  TCRs are needed for regulatory T cells (Tregs) to function, which is a subpopulation of T cells that are responsible for preventing autoimmune disease and maintaining tolerance to self-antigens. These types of T cells have also been shown to recognize microbes. This makes microbe-specific Tregs crucial as they can prevent the host from activated immunopathology.




Understanding the effect of microbe-specific Tregs on anti-pathogen immunity in the presence of these T cells is significant, as it can help us understand more about host immunity against infections. The study found in the Proceedings of the National Academy of Sciences journal looks further into this concept, and aims to identify microbe-specific Tregs in humans in order to determine T cell specificity. This was done using peptide-MHC (pMHC) tetramers, a protocol which uses tetramer-based enrichment to analyze the pre-immune range of CD4+ T cells.  More specifically, using this technique they isolated rare CD4+ T cells, containing a protein called Foxp3,from adult human peripheral blood and noted their frequency.

The findings from the study showed that a percentage of circulating Tregs recognize foreign antigens, and the frequency of these cells is in correspondence to self-reactive Tregs, in the absence of infection. However, the frequency of Tregs that recognize common microbial antigens is drastically reduced in the blood of the majority of adults. The findings suggest that although the specific population of CD4+ T cells in human peripheral blood bears some Tregs at birth, the balance between regulatory T cells and conventional T cells changes due to antigen exposure. The study’s data highlight the importance of antigen specificity as antigen exposure can have a significant effect on the impact of anti-pathogen immunity.

 

By: Sana Issa, HBSc




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