Class II major histocompatibility complex and organ specific autoimmunity in man

Area of Science:

• Immunology
• Autoimmunity
• Cellular Biology

Background:

• T helper lymphocytes require antigen presentation by cells expressing compatible class II major histocompatibility complex (MHC) molecules.
• Normally, target cells in organ-specific autoimmune diseases lack surface class II MHC, preventing antigen presentation and maintaining immune tolerance.
• Aberrant expression of class II MHC on target cells has been observed in several autoimmune diseases.

Purpose of the Study:

• To investigate the role of aberrant class II MHC expression in initiating organ-specific autoimmune diseases.
• To explore the mechanism by which cell-specific antigens are presented to T helper lymphocytes in autoimmunity.

Main Methods:

• The study discusses the immunological principles of antigen presentation and T cell recognition.
• It reviews evidence of aberrant class II MHC expression in target cells of autoimmune diseases.
• The proposed mechanism involves the presentation of cell-specific antigens to autoreactive T helper lymphocytes.

Main Results:

• Aberrant expression of class II MHC on target cells can lead to the presentation of cell-specific antigens.
• This presentation may overcome immunological tolerance to self-antigens.
• Potentially autoreactive T helper lymphocytes can be activated by these presented antigens.

Conclusions:

• Aberrant expression of class II MHC antigens is proposed as a potential initiating factor in certain organ-specific autoimmune diseases.
• The aberrant expression facilitates the presentation of cell-specific antigens, potentially breaking immune tolerance and triggering autoimmune responses.