Mark each statement as either true or false. Rewrite false statements to make them true by changing the underlined words.
__________ MHC class II molecules are found on T cells.

Verified step by step guidance

1. Understand the role and location of MHC class II molecules: MHC class II molecules are primarily found on antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells, not on T cells.
2. Evaluate the given statement: 'MHC class II molecules are found on T cells.' This statement is false because T cells do not express MHC class II molecules on their surface.
3. Rewrite the false statement to make it true by replacing 'T cells' with the correct cell types that express MHC class II molecules.
4. The corrected statement should read: 'MHC class II molecules are found on antigen-presenting cells such as dendritic cells, macrophages, and B cells.'
5. Remember that MHC class II molecules present extracellular antigen fragments to CD4+ helper T cells, which is why they are expressed on APCs and not on T cells themselves.

Key Concepts

MHC Class II Molecules

MHC class II molecules are proteins primarily expressed on antigen-presenting cells like dendritic cells, macrophages, and B cells. They present extracellularly derived peptides to CD4+ helper T cells, initiating immune responses.

Cell Types Expressing MHC Molecules

Different immune cells express distinct MHC classes: MHC class I is found on almost all nucleated cells, while MHC class II is restricted to professional antigen-presenting cells. T cells themselves do not express MHC class II molecules.

Role of T Cells in Immune Response

T cells recognize antigens presented by MHC molecules but do not present antigens themselves. CD4+ T cells interact with MHC class II on antigen-presenting cells, while CD8+ T cells recognize MHC class I on infected cells.