Chapter 14, Problem 1Q

Summary Introduction

Introduction:

The overreactions of the immune system to some non-toxic or innocuous environmental antigens are known as the hypersensitivity reactions. These are also known as allergic reactions. Depending upon the active mechanisms these reactions are grouped into four types.

Answer to Problem 1Q

Correct answer:

The correct answer is option (c) type III hypersensitivity: modified cell-surface components.

Option (g) type II hypersensitivity: immediate hypersensitivity.

Explanation of Solution

Explanation/justification for the correct answer:

Option (c) type III hypersensitivity: modified cell-surface components. Type III hypersensitivity is usually caused by the small and soluble immune complexes of antigen-specific IgG. These are deposited in the walls of blood capillaries or the alveoli of lungs. Antibodies or other proteins are commonly derived from the non-human animal species. These are given to the patients which are prone to type III hypersensitivity reactions. So, the correct answer is option (c).

Option (g) type II hypersensitivity: immediate hypersensitivity. In this type of hypersensitivity, reactions take place immediately after the contact to the allergens. Type II hypersensitivity is also known as immediate hypersensitivity as it leads to immediate allergic reactions. So, the correct answer is option (g).

Explanation for incorrect answer:

Option (a) type I hypersensitivity: mast cells, basophils, and eosinophils. These hypersensitivity reactions are started by the infection of an allergic-antigen with the allergen-specific IgE. These are linked to FceRI receptors of mast cells, basophils, and eosinophils. So, this is an incorrect option.

Option (b) type II hypersensitivity: Penicillin allergy. It is a type of hypersensitivity reactions which is caused by an IgG response to some chemical and small molecules. These are covalently bound to the outside surface of the cells. So, this is an incorrect answer.

Option (d) type IV hypersensitivity:CD4 T_H1 or CD8 T-cells. These reactions are usually caused by the antigen-specific effector T-cells like CD4 T_H1 cells or CD8 T-cells. So, this is an incorrect answer.

Option (e) type III hypersensitivity: non-human therapeutic proteins. Antibodies which are derived from the non-human animal species are usually given to patients. These induce type III hypersensitivity reactions. So, this is an incorrect answer.

Option (f) type IV hypersensitivity: modified intracellular human proteins. These reactions are usually caused by CD4T-cells. These cells respond to the epitopes of peptides which are derived from chemically modified human proteins. The example of these proteins is nickel-modified peptides presented by MHC class II molecules. So, this is an incorrect answer.

Option (h) type I hypersensitivity: IgE cross-linking. This type of hypersensitivity is usually caused by the interaction of soluble allergens with the specific IgE. So, this is an incorrect answer.

Conclusion

Hence, Type III hypersensitivity is usually caused by small soluble immune complexes of antigen and specific IgG. Type II hypersensitivity is also known as immediate hypersensitivity as it leads to immediate allergic reactions. So, the correct answer is option (c) type III hypersensitivity: modified cell-surface components, option (g) type II hypersensitivity: immediate hypersensitivity.