Which of the following statements about the immune system is wrong?
A.
Immunity is brought about by a variety of leukocytes (white blood cells), including macrophages and lymphocytes, all of which develop from undifferentiated stem cells in the bone marrow.
B.
The immune response consists of two complementary systems, the humoral and cellular immune systems. The humoral immune system is directed at bacterial infections and extracellular viruses (those found in the body fluids), but can also respond to individual foreign proteins. The cellular immune system destroys host cells infected by viruses and also destroys some parasites and foreign tissues.
C.
Immunoglobulins bind bacteria, viruses, or large molecules identified as foreign and target them for destruction. Making up 20% of blood protein, the immunoglobulins are produced by B lymphocytes, or B cells, so named because they complete their development in the brain.
D.
Recognition of infected cells or parasites involves proteins called T-cell receptors on the surface of cytotoxic T cells.