This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Type of receptor present on T-cells are: 
Select and explain. 
A. IgA, B. IgG, C. Prostaglandins, D. CD4
D: CD4
Answer: D: CD4 
Explanation: Helper T cells 

Carries CD4 marker.
Helps or induces immune responses.
Recognize antigen in association with class II MHC.
Macrophages are activated to kill intracellular microorganisms by secreting cytokines.

Parija SC. Textbook of Microbiology & Immunology. Elsevier Health Sciences; 2014. Page:127