IgE antibodies in an individual already pre-sensitized to a particular allergen are bound to mast cells before exposure to the allergen. True False Type IV hypersensitivity involves Which cell type is known to play a key role in regulating type IV hypersensitivities, ensuring that they do not get out of control? Solution 4) answer is true usually an interval of 2-3 weks is required between senstizing and shocking dose, during, which cytotropic antibody igE( previously known as reagnic antibody) produced aganist the antigen attached to mast cells. when a shocking dose is given there is rapid stimulation of mast cells. 5) type IV reactions there no production of antibodies. it is cell mediated immunity in wjihc lymphocytes play important role. answer t helper cells also participlate in delayed hypersensitivity reactions answer is Th1, Tc and M0 6) NK cells it is a non T non B cell large granular cell which considered as third type of lymphocyte plays important role in typeIV reactions detroys viruses, virus infeted cells, malignant invaded cells..