Question

Histamine is secreted by
A. Mast cells
B. Histiocytes
C. Lymphocytes
D. Fibroblasts

Answer 1

Hint: Histamine is released as a part of local immune responses to the presence of invading bodies. It is an organic nitrogenous compound. Histamine causes inflammation so that other chemicals are also released out and help in the repair work.

Complete answer:
Basophils and mast cells secreted histamine as a part of the local immune response to cause inflammation. These cells are found in the connective tissues, and mucous membrane. When the histamine is released, this causes the capillaries to become more permeable to the WBC, which will attack the foreign bodies in the affected areas.
Histiocytes are also called macrophages. It is a type of white blood cell, derived by the bone marrow. It degrades phagocytosed antigen protein into the peptide. It also provides the information of antigen to T cells by MHC class II.
Lymphocytes are also a WBC, which help in defending the body against the diseases. Two types of lymphocytes are T cells and B cells. It secreted the lymphokines.
Connective tissues also contain the most common cell called a fibroblast. They secreted collagen protein which helps in the framework of the many tissues.

Hence, the histamine is secreted by the mast cell, so the correct answer is option A. 

Note: In type I allergy, the mast cell plays an important role. They have high-affinity IgE receptors and histamine. Their granules also have the heparin. They are activated when they are encountered by the pathogens or antigen. Mast cell also acts as a neurotransmitter. It plays an important role in the function of the bowel.