Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 111

NK cells acquires antigen-specific memory to
haptens (small molecules that react with protein and can then elicit an immune
response) and viruses [ 214 ]. NK cells from the liver, but not spleen, sensitized
to a given hapten retain memory for this hapten and can mediate hapten-induced
contact hypersensitivity response. Hepatic NK cells also develop specific memory of
vaccines that contain antigens from influenza, vesicular stomatitis, or type-1 human
immunodeficiency virus. The persistence of memory NK cells, but not antigen
recognition, depends on CXCR6 chemokine receptor, instead of pattern recognition
receptors. 100

A subset of hepatic CXCR6 +

3.10 T Lymphocytes

The human hematopoietic system gives rise to all blood cell types, among which
thymic (T) lymphocytes, ot T cells. An exclusion step permits T-cell specification
from lymphoid-committed progenitor cells that themselves result from blockade
of erythroid and myeloid lineage at an early developmental stage, as it supresses
alternative development toward B and NK (natural killer) cells.
Naive T lymphocytes differentiate into mature effector cells that form distinct
T-cell populations and produce a given set of cytokines. The synthesized cytokine
set does not necessarily define the T-cell lineage because the T cell program of
cytokine production can be modified according to circumstances.
Each T lymphocyte is unique, as it is shaped by the environmental factors
encountered during its life. However, T lymphocytes can be grouped into vari-
ous subsets based on their effector function and molecular phenotype. Distinct
T-lymphocyte subsets and differentiation states that can be identified based on ex-
pressed plasmalemmal markers and produced effector molecules promote different
types of immune response. Moreover, T lymphocytes can interconvert from one
subset phenotype to another, although signaling can cause a long-term fixation
of cytokine memory. The phenotype of effector T lymphocytes can actually be
remodeled.
Conventional

T lymphocytes recognize antigens presented in the groove of
classical major histocompatibility molecules via their T-cell receptors. In addition,
classical MHC class-1a and -1-like molecules interact with many other receptors to
control T-cell activation.

αβ

3.10.1 T-Lymphocyte Development

T lymphocytes evolve in the thymus through several developmental stages. Early
thymus-settling progenitors indeed mature through double-negative DN1, DN2, and

100 Whereas 35 to 55% of hepatic NK cells express CXCR6, only 3 to 5% of splenic NK cells
produce this chemokine receptor.