A drug that is a fifth-generation cephalosporin which is the first in its class effective against MRSA is:

A. IgE (Immunoglobulin E): This class of antibodies is primarily involved in hypersensitivity reactions Type I, which are immediate allergic reactions. When a person is exposed to an allergen they are sensitive to, IgE antibodies on the surface of mast cells and basophils bind to the allergen. This triggers the release of inflammatory mediators like histamine, leading to allergic symptoms such as itching, hives, and in severe cases, anaphylaxis.

B. IgA (Immunoglobulin A): IgA antibodies are primarily found in mucosal areas such as the respiratory and gastrointestinal tracts. They play a role in immune defense on mucosal surfaces and are important for preventing infections. While IgA is not directly associated with hypersensitivity reactions Type I, deficiencies in IgA can sometimes lead to increased susceptibility to certain infections.

C. IgG (Immunoglobulin G): IgG antibodies are the most common type of antibody in the bloodstream and are involved in various immune responses, including defense against bacterial and viral infections. IgG antibodies are not specific to Type I hypersensitivity reactions; they are part of the immune system's broader defense mechanisms.

D. IgM (Immunoglobulin M): IgM antibodies are the first antibodies to be produced in response to an infection. They are large pentameric molecules and are effective at agglutinating pathogens. IgM antibodies are involved in the primary immune response to infections, but they are not specifically associated with Type I hypersensitivity reactions.

A. IgD: Immunoglobulin D (IgD) is found on the surface of B cells and serves as a receptor for antigen recognition during the immune response. Its exact function is not fully understood, but it plays a role in the activation of B cells.

B. IgE: Immunoglobulin E (IgE) is primarily associated with allergic responses and defense against parasitic infections. When an allergen enters the body, IgE antibodies trigger the release of histamine and other chemicals, leading to allergy symptoms. IgE is also involved in protecting against certain parasites.

C. IgG: Immunoglobulin G (IgG) is the most abundant immunoglobulin in the bloodstream. It provides long-term immunity by recognizing and neutralizing pathogens such as bacteria and viruses. IgG antibodies are involved in secondary immune responses and are transferred from mother to fetus, providing passive immunity.

D. IgM: Immunoglobulin M (IgM) is the first antibody produced during an initial immune response to an antigen. It is effective at agglutination (clumping) of pathogens. IgM antibodies are generally found in blood and lymph fluid and are the first line of defense during infections.