Oh, Look…More Lymphocytes

Beyond T cells, B cells, and innate lymphoid cells (ILCs), there are other lymphocyte populations that play important roles in the immune system. Some examples include:

1. Natural Killer (NK) Cells:
   • NK cells are lymphocytes that are part of the innate immune system. They play a crucial role in the detection and elimination of virus-infected cells and certain tumor cells. NK cells do not rely on antigen specificity and can recognize and destroy target cells based on the absence or alteration of specific surface molecules.
2. Gamma Delta (γδ) T Cells:
   • Gamma delta T cells are a subset of T cells that express a unique T cell receptor (TCR) composed of gamma and delta chains. Unlike conventional αβ T cells, which recognize peptide antigens presented by major histocompatibility complex (MHC) molecules, γδ T cells can recognize non-peptide antigens, including lipid and metabolite antigens. They play roles in immune responses at epithelial surfaces and can exhibit both innate and adaptive immune functions.
3. Mucosal-Associated Invariant T (MAIT) Cells:
   • MAIT cells are a specialized subset of T cells that express a semi-invariant TCR. They are particularly abundant in mucosal tissues, such as the gut. MAIT cells recognize microbial metabolites presented by a non-classical MHC-like molecule called MR1. They are involved in the defense against bacterial infections.
4. Double-Negative (DN) T Cells:
   • Double-negative T cells are a subset of T cells that lack both CD4 and CD8 co-receptors. They are found in various tissues, including the thymus, and can exhibit diverse functions. Some DN T cells are involved in regulatory functions, while others may have cytotoxic properties.
5. Lymphoid Tissue-Inducer (LTi) Cells:
   • LTi cells are a specialized subset of lymphocytes that play a crucial role in the development of lymphoid tissues during embryogenesis. They contribute to the formation of lymph nodes and Peyer’s patches in the gut.
6. Intraepithelial Lymphocytes (IELs):
   • IELs are lymphocytes located within the epithelial layer of various tissues, particularly the intestinal epithelium. They contribute to the surveillance of epithelial surfaces and play roles in mucosal immunity.
7. Regulatory T Cells (Tregs):
   • Regulatory T cells are a subset of CD4+ T cells that play a critical role in immune regulation and tolerance. They suppress the activity of other immune cells, helping to prevent excessive immune responses and autoimmune reactions.

End of Section 1.6

Next Topic: Sending a Message Near and Far

Source: ChatGPT response prompted and edited by Joel Graff.

• Immunology (Table of Contents for Entire Course – FREE!)
  • Other content for Unit 1: Introduction to Immunology