Question

Compare and contrast how the innate and adaptive immune systems distinguish self from non-self. How does the innate immune system distinguish a foreign invader from a self cell? What cells and molecules are involved? How specific is the detection, and what is the source of the specificity? How does the adaptive immune response distinguish a foreign invader from a self cell? What cells and molecules are involved? How specific is that detection, and what is the source of the specificity?

Please be as clear and specific in your explantion.

Answer 1

The cells of innate immune system recognizes specific Pathogen associated molecular patterns(PAMPs) that are unique to pathogens and is not present on self cells. These PAMPs are recognised by Toll like receptors and Pathogen recognition receptors present on the surface of phagocytes leading to their activation, producing cytokines and amtimicrobial peptides in response to the pathogen. The cells of innate immunity (such as Natural killer cells) recognises and kills abnormal cells that have reduced expression of class I MHC and does not recognizes a normal cell which expresses normal levels of class I MHC as virally infected and tumor cells downregulates MHC. Innate immune system involves the phagocytes: Neutrophills, macrophages, neutrophils that recognises and engulfs pathogens. Innate immune system is non-specific and targets a broad range of pathogens.

Adaptive immune system on the other hand includes T and B lymphocytes and recognizes antigens through receptors (T cell receptors and B cell receptors) that are specifically tailored against the antigen. During their development, B and T cells are exposed to self antigen in the primary lymphoid antigens. The cells which binds strongly to these self antigens or autoreactive cells are eliminated through apoptosis and prevents the generation of self reactive lymphocytes. The T cell receptors(TCR) recognizes processed peptides from the antigens that are complexed with Class I or II MHC, on the surface of host cells whereas B cells binds to native antigen through their B cell receptors(BCR) or membrane bound antibody molecule. The adaptive immune response is highly specific and can recognize a vast repertoire of antigens by generating diversity in BCR and TCR through genetic recombination.