Question

what type of cell activated cd4 T cells?

-B cells

-Mast cell

-Macrophages and DC

Answer 1

Ans) Macrophages and DC

Explaination: CD4+ T cells or T helper cells are activated by professional antigen presenting cells (APCs) e.g.  macrophages, dendritic cell (DC)and B cells. MHC class II molecules are expressed on professional APCs .Dendritic cell express MHC class II molecules constitutively and most efficient as antigen presenting cells while others such as macrophage and B cell need to be activated before they can function as APCs  that's why option that include debdritic cell and macrophages is the right answer to this question.

MHCII molecules bind the exogenous peptide antigens and present it to T helper cells which get activated and then help both Bcells and cytotoxic T cell (CD8+T cell) to develop humoral and cellular immune response respectively.

Mast cells are part of proinflammatory response which secrete histamines , heparin, TNFα ,IL-4,5,6 and mediate allergic reactions but play no direct role in activation of CD4+ T cell.