Question

put the steps into the correct order to trace the process of immunity

1. upon subsequent contact with the same antigen, circulating specific antibodies combine with antigens to form a lock and key complex, triggering an immediate call to the phagocytes
2. the first time an antigen is seen, phagocytes engulf antigens and present them to helper t lymphocytes
3. helper t lymphocytes secrete lymphokines and activate and stimulate divisions of t and b lymphocytes
4. t lymphocytes produce killer and memory t lymphocytes. b lymphocytes produce plasma cells and memory b lymphocytes

Explanation:

The immune response starts with phagocytes engulfing and presenting antigens to helper T - lymphocytes. Then helper T - lymphocytes secrete lymphokines to activate T and B lymphocytes. T and B lymphocytes differentiate into various cell types. Subsequent contact with the same antigen leads to the antibody - antigen complex formation and phagocyte recruitment.

Answer:

2, 3, 4, 1