Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 154

Most NK cells in lymph nodes and tonsils are CD56 high ,CD16 with CCR7

expression, but lack KIRs and have a low intracytoplasmic perforin content. They
secrete large amounts of cytokines (Ifn

−

γ , CSF2, and TNFSF1). Some human

CD56 high ,CD16 chain (CD127). They are characterized

by an enhanced cytokine production with a T H1 cytokine expression pattern.

− NK cells express IL7R α

3.11.5.5 Regulators of NK-Cell Activity

Various substances stimulate or inhibit NK-cell activity. Type-I interferons and
interleukin-12, -15, and -18 are potent activators of NK cells. Interleukin-2 promotes
NK-cell proliferation, cytotoxicity, and cytokine secretion. Transforming growth
factor-

β

and IL10 are inhibitors. Memory T and NK cells that express IL23R and

γ

ROR 2 (NR1f3-2) constitutively synthesize IL17 rapidly and independently of IL6,

in contrast with T H17 cells [ 283 ].

3.11.5.6 Immunological Memory

Immunological memory is characterized by the long-term persistence of memory
cells that rapidly undergo clonal expansion and enhanced effector function in
response to new challenges, especially viral infections. About 2 months after initial
infection, memory NK cells can be detected in nearly all organs (spleen, lymph
nodes, liver, lung, and kidney) [ 276 ].

3.12 B Lymphocytes

Bone marrow (B) lymphocytes, or B cells, are responsible for the humoral
(antibody-mediated) immunity. B lymphocytes are component of the adaptive
immunity via synthesized, relevant antibodies. B lymphocytes produce immunoreg-
ulatory antibodies against antigens. Each B lymphocyte possesses a unique
plasmalemmal B-cell receptor (BCR), a membrane-bound immunoglobulin, that
can bind to a cognate antigen.
B lymphocytes develop in the liver of fetuses and in the bone marrow of adults
from hematopoietic stem cells. All B lymphocytes derive from a particular cell
(clone). They recognize and bind the same component of a given antigen. The huge
number of clones explains the wide range of detected antigens.
Naive B lymphocytes will meet antigens for the first time. In the absence
of antigen, B lymphocytes are at rest, but they are not inactive. These antigen-
presenting cells mature after activation by antigen. Antigens recruit antigen-specific
cells from the pool of mature B lymphocytes. Once a B lymphocyte encounters its
cognate antigen and receives an additional signal from a helper T lymphocyte, it
differentiates into either a plasmocyte or memory B cell.