Select the correct statement about lymphocytes.

(A) B cells produce plasma cells, which secrete antibodies into the blood.

(B) The two main types are T cells and macrophages.

(C) T cells are the precursors of B cells.

(D) T cells are the only form of lymphocyte found in lymphoid tissue.

(A) B cells produce plasma cells, which secrete antibodies into the blood.

Explanation:

Lymphocytes are one of several types of defense cells in the body and belong to a group of cells called leukocytes or white blood cells. These cells are produced in the bone marrow and defend the body against disease, infection or allergies. Lymphocytes, in particular, are usually increased when there is an infection and their amount serves as an indicator for various diseases such as influenza, allergy, toxoplasmosis, rubella, leukemia and even HIV.

There are several types of lymphocytes in the human body. Antibodies are produced by B cells (also called B lymphocytes) and have the ability to specifically combine with foreign substances in the body, inactivating them. Antigens are extremely specific, so we can say that for each of its types there is a type of antibody, complementary to that of the antigen.

Lymphocytes are the agranular cells of WBC. These are mainly 2 types - T lymphocyte and B - lymphocytes. Natural killer cells / NK cells are also another type of lymphocyte. The lymphocytes are present in both blood and lymph. They play are responsible for both innate and adaptive immunity.

The natural killer cells are meant for both innate immunity and adaptive immunity. The T cells and B cells are responsible for adaptive immunity.

The humoral immunity is mediated by B cells while T cells are mediated the cell-mediated immunity. When an antigen enters into the body the B cells get to activate and it becomes effector B cells. These B cells are proliferated by mitosis and produce plasma cells. Plasma cells have antibodies which provide adaptive immunity.

Both the B lymphocytes and T lymphocytes are synthesized in the bone marrow. This process is called hematopoiesis. Then these 2 types of cells are separated and mature in different cells. Therefore, bone marrow is the precursor of B cells and T cells.

B lymphocytes are matured in bursa or MALT cells, while the T lymphocytes are matured in the thymus.

T cells are not the only form of lymphocytes found in lymphoid tissues. The lymphoid tissues are - bone marrow cells, WBC, thymus, spleen, lymph nodes. Macrophages are the larger WBC and one form of monocytes.