PATHOLOGY

Detailed explanation-1: -So, the correct answer is ‘Mast cells’.

Detailed explanation-2: -Histamine released from mast cells and basophils exerts its biological activities by activating four G protein-coupled receptors, namely H1R, H2R, H3R (expressed mainly in the brain), and the recently identified H4R.

Detailed explanation-3: -The cell is localized perivascularly in the loose connective tissue. The mast cell secretes histamine by exocytosis when it is stimulated immunologically by binding of a specific antigen to IgE molecules in the cell membrane.

Detailed explanation-4: -Histamine is a neurotransmitter that is released from histaminergic neurons which project out of the mammalian hypothalamus. The cell bodies of these neurons are located in a portion of the posterior hypothalamus known as the tuberomammillary nucleus (TMN).

Detailed explanation-5: -In the skin, antigens, via IgE, activate mast cells in the deep layers of connective tissue. Mast cells release histamine as well as other vasoactive molecules, which cause urticaria (hives). If the antigen activates mast cells in deeper tissue, this can lead to angioedema.