All of the following except one are CD⁴⁺ cells:

The correct answer is T-­cyto toxic cells.

Key Points

• T-cytotoxic cells, also known as cytotoxic T lymphocytes (CTL), are generally CD8+ cells, not CD4+.
• They are primarily responsible for targeting and killing infected cells in the body.
• So, T-cytotoxic cells are the one that does not belong in the list of CD4+ cells.

Additional Information

• CD4+ T-Helper Cells: CD4 is a glycoprotein found on the surface of these immune cells. As their name suggests, T-helper cells assist other cells in the immune system, including B cells and cytotoxic T cells, to perform their functions effectively. They are a critical part of the adaptive immune system.
• Monocytes and Macrophages: These cells also have the CD4 receptor on their surface. Monocytes are a type of white blood cell that can differentiate into macrophages and dendritic cells, which are key players in the immune system. Macrophages, known for their phagocytic (microbe-eating) capabilities, are strong, nonspecific defense mechanisms against invading microbes.
• CD8+ Cytotoxic T cells (T-cytotoxic cells): Cytotoxic T cells are crucial for immune defense against intracellular pathogens (like viruses) and for tumor control. Different from T-helper cells, these cells express the CD8 glycoprotein on their surface, hence not considered as CD4+ cells. After interacting with infected or malignant cells, cytotoxic T cells release molecules like perforin and granzymes that kill the target cells.