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Antigen presentation
Make it clearer
The immune system does not see whole microbes: it sees fragments. An antigen is that fragment, a piece of something that can be recognized. And something has to display it. Dendritic cells, defense cells with branch-like projections, pick up the fragment and display it on molecules called the major histocompatibility complex, or MHC. That display activates T cells, the white blood cells that direct and carry out the response.
There are two different display cases: one on every cell, the other on presenting cells. Class I sits on every cell with a nucleus and shows what was made inside, to CD8 T cells. Class II sits on presenting cells and shows what was picked up outside, to CD4 T cells.
The molecules that make up those display cases are encoded by the HLA genes, and they help distinguish self from non-self. In T cell mediated transplant rejection, the T cell recognizes the HLA-peptide complex of the donor, the person the organ came from.
In brief
In antigen presentation, dendritic cells display the antigen on major histocompatibility complex molecules to T cells.
Class I MHC, on every nucleated cell, shows internal antigens to CD8 cells; class II, on presenting cells, shows external ones to CD4 cells.
Two display cases: one on every cell, the other on presenting cells.
HLA genes encode molecules that help distinguish self from non-self; in T cell mediated rejection, the T cell recognizes the donor HLA-peptide complex.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Active Immunity, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingBiochemistry, HLA Antigens, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated