If the following features were put in chronological order which would come fourth?

The answer is B. Exposure to antigen (A) results in stimulation of (E) the cells in the superficial cortex of the lymph node (germinal centre cells); these cells enlarge and develop into B-immunoblasts (C) which divide and some differentiate into plasmablasts (B), which mature into plasma cells (D). A proportion of the B-immunoblasts differentiate into B memory cells and join the circulating pool of small lymphocytes.