The book "Kuby Immunology" states that normal infected cells might present antigenic peptides on their surface via MHC class I, but these can't activate naive CD8 cells. Only infected professional antigen presenting cells have the necessary co=stimulatory signals to do so. This is why cross presentation happens. But then why does the process of antigen presentation on normal infected cells happen then, if it is of no use?

  • $\begingroup$ "This is why" cross presentation happens - is not my understanding. This is why presentation happens, by the professionals (APCs). Your question refers to presentation by APC in contrast to normal body cells that are not part of the immune system, right? Cross-presentation is a special form of presentation by "antigen presenting cells" - APC. It occurs to me: normal cells present antigen, however may not be called antigen presenting cells. And, please correct: normal cells do not present on MHCII, hence do not cross-present. $\endgroup$ Dec 17, 2020 at 16:43

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It is of use. They're saying that naive T cells cannot be activated by normal cells because the latter lack the appropriate co-stimulus, namely B7. However, activated CD8+ T cells can recognize antigens presented by normal cells and form a response. This is how cytotoxic T cells are able to eliminate transformed or infected cells.


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