Q.(a) How will a doctor identify that the host body has rejected a graft ? OR

(a) Graft rejection shows up as inflammation, declining organ function, and immune-cell infiltration of the transplant. (b) Honey bees live in castes -- queen, workers, drones -- whose life cycles and roles are mutually dependent.

(a) Graft rejection occurs because the recipient's immune system recognises the transplanted tissue's surface antigens (MHC molecules) as foreign and mounts a T-cell-mediated attack against it; clinically, a doctor suspects rejection when the transplant site shows swelling, tenderness and pain, the patient develops fever, and laboratory tests show declining function of the transplanted organ (for instance, rising blood creatinine and reduced urine output after a kidney transplant, indicating the new kidney is failing). Definitive confirmation comes from a tissue biopsy of the graft, which under the microscope shows infiltration by the recipient's own lymphocytes attacking the donor tissue -- the hallmark of an active rejection episode. (b) A honey bee hive is organised into three castes that depend entirely on one another: the queen is the sole reproductive female, mated once and then laying all the eggs for the colony's entire life; the workers are sterile females that perform all the colony's labour through their lives -- young workers clean cells and feed larvae and the queen, older workers build and repair comb, guard the hive, and finally forage for nectar and pollen; and the drones are males whose only function is to mate with a new virgin queen (after which they die), contributing no labour to the hive. The colony functions as a single unit only because e …