This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of skin, Subject name: Dental
CD 56 is a marker for which cells 
Select and explain. 
A. B Lymphocytes, B. T Lymphocytes, C. Eosinophils, D. NK cells
D: NK cells
Answer: D: NK cells 
Explanation: NK-cells :- # Key component of the innate immune system . # Lack T-cell receptors or immunoglobulins. # Cell surface markers include CD2, CD56, and CD16 . # Identify infected (viral) or tumor cells that have decreased MHC I surface expression and destroy these cells perforin/granzymes. # Secrete IFN-g that can enhance the phagocytic capability of macrophages and have cytoplasmic granules that have a similar mechanism to cytotoxic T-lymphocytes. # NK-cells are activated by IL-12, IL-15, and type I interferons. # Work synergistically with macrophages. Ref:- Review of Dermatology by Alikhan; pg num:-23