Chapter 9 Lymphocytes Flashcards
Lymphocytes are divided into three major groups:
T cells, B cells, and natural killer (NK) cells
major players in adaptive immunity
T and B cells
make up a small percentage of lymphocytes and are part of innate immunity
NK cells
Adaptive immunity has three characteristics:
It relies on an enormous number of distinct lymphocytes, each having surface receptors for a different specific molecular structure on a foreign antigen;
after an encounter with a particular antigen, memory cells are produced that will react faster and more vigorously to that same antigen on reexposure;
self-antigens are “ignored” under normal circumstances (referred to as tolerance).
Antibody-producing lymphocytes are called
because they develop in the bone marrow
B lymphocytes or simply B cells
Cellular immunity is accomplished by two types of lymphocytes:
T cells and NK cells
develop in the thymus
T cells
develop in both the bone marrow and the thymus
NK cells
- Lymphocytes are not end cells. They are resting cells, and when stimulated, they undergo mitosis to produce both
memory and effector cells.
- Unlike other leukocytes, lymphocytes recirculate from the blood to the ________ and back to the blood.
tissues
- B and T lymphocytes are capable of rearranging antigen receptor gene segments to produce a wide variety of
antibodies and surface receptors
- Although early lymphocyte progenitors such as the common lymphoid progenitor originate in the bone marrow, T and NK lymphocytes develop and mature
outside the bone marrow
Lymphocytes make up between 18% and 42% of circulating leukocytes with an absolute number of
0.8 to 4.8 X 10 to the power of 9/L
development occurs in the bone marrow and thymus (sometimes referred to as central or primary lymphatic organs)
Antigenindependent lymphocyte
development occurs in the spleen, lymph nodes, tonsils, and mucosa-associated lymphoid tissue such as the Peyer’s patches in the intestinal wall (sometimes referred to as peripheral or secondary lymphatic organs)
antigen-dependent lymphocyte
develop initially in the bone marrow and go through three stages known as pro-B, pre-B, and immature B cells.
B lymphocytes
It is during these stages that immunoglobulin gene rearrangement occurs so that each B cell produces a unique
immunoglobulin antigen receptor
which have not yet been exposed to antigen (antigen-naive B cells), leave the bone marrow to migrate to secondary lymphatic organs, where they take up residence in specific zones such as lymph node follicles.
immature B cells,
These immature B cells, also known as
hematogones
have a homogeneous nuclear chromatin pattern and extremely scanty cytoplasm
hematogones
These cells are normally found in newborn peripheral blood and bone marrow and in regenerative bone marrows.
hematogones
Leukemic cells from patients with (ALL) can sometimes resemble hematogones
acute lymphoblastic leukemia
where B cells may come in contact with antigen, which results in cell division and the production of memory cells as well as effector
secondary lymphatic organs or in the blood
Effector B cells are antibody-producing cells known as
plasma cells and plasmacytoid lymphocytes
