Which of the following statements accurately describes immunity?

Administration of preformed antibodies is necessary to treat a viper snake bite.

Explanation:

(a) In the case of a viper snake bite, the administration of preformed antibodies is an effective treatment. These antibodies, called antivenom, are obtained from animals that have been immunized against snake venom. When injected, these preformed antibodies can neutralize the venom and provide immediate protection.

(b) The production of antibodies against the smallpox pathogen is primarily carried out by B-lymphocytes, not T-lymphocytes. B-lymphocytes are responsible for recognizing the pathogen and generating specific antibodies that can target and eliminate it.

(c) Antibodies are composed of two heavy chains and two light chains, not four light chains. The arrangement of these chains gives antibodies their characteristic Y-shaped structure, with two heavy chains and two light chains forming each arm of the Y.

(d) The rejection of a kidney graft or transplant is primarily mediated by T-lymphocytes, specifically cytotoxic T-cells. These cells recognize foreign antigens on the transplanted kidney and mount an immune response to eliminate it. B-lymphocytes play a role in antibody production, which can contribute to the rejection process indirectly.

Therefore, the correct statement regarding immunity is: (a) Preformed antibodies need to be injected to treat the bite by a viper snake.