Question

Dendritic cells take up, process or present antigen by all of the following routes except _____.

a. receptor-mediated endocytosis of bacteria
b. macropinocytosis of bacteria or viruses
c. uptake of viruses using Toll-like receptor TLR9
d. cross-presentation from the MHC class II pathway to the MHC class I pathway
e. cross-presentation from incoming infected dendritic cells to healthy resident dendritic cells in secondary lymphoid tissue
f. delivery of viral peptides from cytosol to endoplasmic reticulum during viral infection.

Answer 1

Dendritic cells do not uptake viruses using Toll-like receptor TLR9; this is the correct answer to the question. They use several other methods such as receptor-mediated endocytosis, macropinocytosis, and cross-presentation to process and present antigens.

Step-by-step explanation:

Dendritic cells take up, process, or present antigen by various mechanisms, but they do not uptake viruses using Toll-like receptor TLR9. The correct answer to the question is: Dendritic cells take up, process or present antigen by all of the following routes except 'uptake of viruses using Toll-like receptor TLR9'.

Receptor-mediated endocytosis is one of the ways through which dendritic cells can internalize bacteria. This involves cell surface receptors that bind to specific components on the bacteria. Another method is macropinocytosis, where the dendritic cell engulfs large volumes of extracellular fluid, which may contain bacteria or viruses.

The concept of cross-presentation refers to dendritic cells presenting antigens on MHC class I molecules that are typically associated with MHC class II pathways or coming from other infected dendritic cells.

Antigen presentation involving MHC II is particularly important for exogenous pathogens like bacteria that are taken into cells and processed through the endomembrane system, while cross-presentation allows dendritic cells to stimulate cytotoxic T cells against these external pathogens.