Class I HLA molecules are found on:

Correct answer: All nucleated cells. Class I HLA (MHC-I) molecules are found on almost all cells that have a nucleus.

Background: HLA stands for Human Leukocyte Antigen.

• B & T cells: B and T cells carry them, but they are not the only cells that do.
• Red blood cells: Red blood cells have no nucleus and carry almost no class I HLA.
• Platelets only: Platelets are not the only cells that carry them.

Did you know? They help the immune system recognise infected cells.

Memory trick: Class I = all nucleated cells.