Question

Please select all of the correct answers in this question to test your understanding of Type 4 hypersensitivity.

• Type 4 hypersensitivity is also referred to as delayed hypersensitivity.

• The severity of the reaction depends upon whether IgG, IgM, or IgE are involved.

• Type 4 hypersensitivity is mediated by T-cells and the effector cells that they recruit.

• Type 4 hypersensitivity is most appropriately treated with antihistamines.

• Type 4 hypersensitivity may result from mismatched blood transfusions.

Answer 1

^{Following are the correct answers in relation to type 4 hypersensitivity.}

1. Type 4 hypersensitivity is also referred to as delayed hypersensitivity : It takes 2 to 3 days for the reaction to develop after exposure to the particular substance, so it is referred to as delayed hypersensitivity
2. Type 4 hypersensitivity is mediated by T-cells and the effector cells that they recruit : Type IV hypersensitivity is characterized by cell-mediated response rather than antibodies as in other types of hypersensitivity reactions. Specifically, the T lymphocytes are involved in the development of the sensitivity, hence called cell-mediated hypersensitivity. T lymphocytes are white blood cells in the body. After exposure to antigens, through a series of biochemical events, the T-cells will be activated.  the T cells activate other white blood cells to mount an immune response.It involves activated T cells, which release cytokines and chemokines, and macrophages and cytotoxic CD8⁺ T cells that are attracted by these moietis.
3. Type 4 hypersensitivity is most appropriately treated with antihistamines : Antihistamines suppress the histamine-induced wheal response (swelling) and flare response (vasodilation) by blocking the binding of histamine to its receptors or reducing histamine receptor activity on nerves, vascular smooth muscle, glandular cells, endothelium, and mast cells.

Answers that are not correct in understanding type 4 hypersensityvity.

1. The severity of the reaction depends upon whether IgG, IgM, or IgE are involved : Type IV hypersensityvity reaction  is not antibody-mediated but rather is a type of cell-mediated response. This response involves the interaction of T-cells, monocytes, and macrophages. Ig E involved in type I,Ig G invoved in type II and type III and the Ig G involved in type II also.
2. Type 4 hypersensitivity may result from mismatched blood transfusions: Type II hypersensitive reactions involve antibody-mediated destruction of cells. This type of reaction is best seen by blood-transfusion reactions, in which host antibodies react with foreign antigens on the incompatible transfused blood cells and mediate destruction of these cells.