Hematopoiesis - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 48

HSC

IL3

lymphoid SC

IL3
IL7

pre−proB lymphocyte LGL CD4+CD8+ TCR

proB lymphocyte

large preB lymphocyte

CD4+CD8+ TCR αβ

small preB lymphocyte

immature B lymphocyte

mature B lymphocyte

NK lymphocyte

CD4−CD8−TCR αβ

CD4+CD8− TH lymphocyte CD4−CD8+ Tsuppressor

TCR αβ

antibody producing
IgM secreting
B lymphocyte

plasmacyte memory B lymphocyte

Fig. 2.6 Formation of lymphocytes. Interleukins act on lymphocyte production. T lymphocytes
include: CD4 + ,CD8 − helper (T H ) T lymphocytes; CD4 − ,CD8 + cytotoxic T lymphocytes;

CD4 − ,CD8 − αγ T lymphocytes; and natural killer (NK) lymphocytes. Plasmalemmal T-cell

receptor (TCR) αβ and γδ chains characterize lymphocyte subpopulations [ 91 ]. Normal CD4 + ,

CD8 . Lymphocytes that express CD8 can be

subdivided into distinct classes according to TCR chain expression pattern. CD4

− lymphocytes have more than 99% of TCR αβ

− ,CD8 +

lymphocytes express predominantly (99%) TCR αβ receptors. CD4 − ,CD8 − lymphocytes have

the highest proportion (62%) of TCR γδ receptors.

2.4.2.8 Other Cytokines

Tumor-necrosis factor- stimulates granulopoiesis and inhibits erythropoiesis.

Interleukins are also involved in hematopoeisis (Fig. 2.6 ).
Interleukin-1 increases the production of colony stimulating factors and stem
cell growth factor. Expression of IL2 is induced by IL1 agent. Interleukin-3 acts on
hematopoietic progenitors, in combination with other cytokines. It induces prolif-
eration of several lineages and enhances the effects of gmCSF factor. Interleukin-4
is a T-cell growth factor and promotes the differentiation of T H0 precursors toward
the T H2 lineage. Interleukin-5 influences eosinophil and basophil production and
functioning. It enhances IL2-dependent differentiation and proliferation of T cells.
Interleukin-6 promotes development and functioning of lymphocytes and meg-
akaryocyte maturation. Interleukin-7 acts on the lymphocyte production, as it
stimulates stem cells to form lymphoid progenitors (Fig. 2.6 ). Interleukin-8 is a
chemoattractant for fibroblasts, neutrophils, basophils, T lymphocytes, and endothe-
lial cells. It also activates integrins in monocytes and eosinophils for extravasation.
Interleukin-9 acts on erythroid progenitors. Interleukin-10 inhibits the synthesis of

α