Answer
All the characterizations pertain to T-lymphocytes (t-cells); therfefore "e" is correct.
Work Step by Step
Differentiation of lymphocytes in the thymus produces many (millions) types of T-cells, each with cell membrane receptors (BCR) specific for one type of antigen.
T-cells differentiate into two main types--cytotoxic T cells (Tc) and helper T cells (Th) cells. When a cytotoxic T-cells meets a microbe infected cell ( APC/macrophage), the Tc cell (TCR) binds with the antigen on the surface of infected cells and forms clones of many activated Tc cells and memory Tc cells.
After Tc cells bind to infected cells , the cytotoxic T-cells secrete perforins that punch holes in the target infected cells; granzymes (enzymes) from the activated Tc cells then pour into the infected cells through the pores; the result is that the infected cells die by apoptosis..
Cytotoxic T cells recognize antigens presented by major histocompatibility complex protein I (MHC I); if the antigen is presented in the groove of a MHC II molecule, the T cell will differentiate into a T helper (Th) cell -- activated T helper cells and T-helper memory cells. In either case, T cells need the assistance of APCs ( macrophages, dendritic cells) to become activated. Helper (Th) cells secrete cytokines that regulate some B-cell activities. In fact
both T helper cells (CD4+) and T regulatory (CD4+T or Treg regulate aspects of B-cell immune activities.
