Question

Empty MHC class I and MHC class II molecules are rapidly removed from

the cell surface. This process prevents:

A. The accumulation of empty MHC molecules on the cell surface which would interfere with T cells recognizing pathogen-derived peptide:MHC complexes
B. Pathogens from evading the immune response by inducing peptide release from cell surface MHC molecules
C. MHC class I molecules from being internalized into endosomes and binding
endosome-derived peptides
D. HLA-DM from trafficking to the cell surface with MHC class II
E. Inappropriate T cell recognition of healthy cells that are not infected, nor have ingested a pathogen

Answer 1

The rapid removal of empty MHC class I and MHC class II molecules from the cell surface is critical for preventing the interference of T cell recognition of pathogens and ensuring proper immune surveillance. MHC I molecules signal cellular health and present intracellular pathogen antigens, while MHC II molecules on antigen-presenting cells activate T cells with exogenous antigens.

Step-by-step explanation:

Empty MHC class I and MHC class II molecules are rapidly removed from the cell surface as a mechanism to ensure efficient immune surveillance and prevent inappropriate immune responses.

This process prevents A. The accumulation of empty MHC molecules on the cell surface which would interfere with T cells recognizing pathogen-derived peptide:MHC complexes.

Removal of empty MHC molecules ensures that T cells are presented with proper antigens for recognition and response.

MHC class I molecules present endogenous antigens (from within the cell, such as those from intracellular pathogens like viruses) and are expressed on almost all nucleated cells, signifying cellular health or pathogen infection.0.

In contrast, MHC class II molecules present exogenous antigens (from outside the cell, such as those from bacteria and parasites) and are expressed only on antigen-presenting cells like macrophages, dendritic cells, and B cells, playing a crucial role in the initial activation of T cells.

The efficient cycling of MHC molecules ensures that each cell presents a dynamic and current snapshot of its internal health, enabling the immune system to promptly detect and respond to infections or abnormal cell activity.

Answer 2

Empty MHC molecules are quickly removed from the cell surface to prevent interference with immune system responses, inappropriate internalization and presentation of non-pathogenic peptides, and T cell recognition of healthy cells.

Step-by-step explanation:

The process of rapidly removing empty MHC class I and MHC class II molecules from the cell surface prevents a number of potential issues in immune response regulation.

One primary concern is avoiding the accumulation of empty MHC molecules, which could potentially interfere with T cells recognizing pathogen-derived peptide:MHC complexes. This interference could thwart the immune system's ability to efficiently identify and react to cells presenting pathogenic peptides.

Moreover, if these empty MHC molecules were present, they could be incorrectly internalized into endosomes, potentially leading to the display of endosome-derived peptides, which would be irrelevant for T cell signaling.

Furthermore, the rapid removal of empty MHC molecules helps prevent inappropriate T cell recognition of healthy cells that are not presenting any pathogen antigens. This is critical for maintaining self-tolerance and preventing autoimmune responses.