MHC I molecules are present on all nucleated cells in humans, while MHC II molecules are found on antigen-presenting cells like macrophages. Antigen-presenting cells (APCs) specifically express MHC II molecules to present antigens. MHC I is vital for detecting infected or cancerous cells, while MHC II is crucial for activating the adaptive immune response. ;
MHC I molecules are found on all nucleated cells in humans, while MHC II molecules are specific to antigen-presenting cells like macrophages. Antigen-presenting cells (APCs) express MHC II to help initiate immune responses. Therefore, the correct option is MHC I molecules.
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