Hormones Affecting
Blood Cell Production &
Function
I. Hormones
A. Erythropoietin
B. Leukopoietin
C. Thymosin
II. Erythropoietin
A. Structure
1. 165 amino acid glycoprotein, MW = 30,000
B. Produced primarily by peritubular capillary
endothelial cells (Kidney)
1. Minor production by Liver
C. Receptor with a single transmembrane domain
1. Requires dimerization like PRL/GH receptor
2. Binds to and activates JAK-2
D. Erythropoietin Action
1. In concert with other growth factors
a) Stimulates growth and maturation of erythroblast
line
b) Stimulates growth of megakaryocyte
c) Stimulates the initiation of megakaryocyte process
formation
E. Erythropoietin Control
III. Leukopoietin
A. Postulated to Exist
B. Stimulate production of Myeloid cells.
IV. Thymic Hormones
A.
History
1. Thymic ablation in adult animals had no
observable effect.
2. Neonatal Thymectomy
a) Wasting Disease
b) Death from opportunistic infections
3. Wasting Disease also after radiation &
thymectomy.
4. Wasting Disease prevented by thymic extracts-Thymosin
B. Thymosins
1. Thymosin Fraction 5:
a) Crude preparation of 40-60 peptides
b) Enhances natural killer cell (NK-cell) activity.
c) Stimulates secretion of Interleukin-2 (IL2)
production
d) Stimulates IL2 receptor expression
e) Stimulates IL1 and tumor necrosis factor (TNF)
production
2. Thymosin-alpha-1
a) 28 amino acid peptide
b) 113 amino acid prohormone, prothymosin alpha
c) Induces differentiation of T-cell precursors
d) Stimulates production of IL2, IL2 receptor & Bcell growth factor
e) Helper (CD4+) and cytotoxic (CD8+) T-cells are
target
f) Increases efficiency of antigen presentation by
antigen presenting cells
g) Paracrine/autocrine factor
h) Regulation not known
3. Beta-thymosins
a) Group of related proteins who’s effect on
lymphocytes is poorly understood
b) May be induced by interferon
c) Thymosin-Beta-4 acts on differentiation and
maturation of early T-cells
d) Many of the beta-thymosins are expressed by
tumor cells and may be involved in metastasis.
C. Other Thymic Peptides
1. Thymostimulin (TP-1)
a) Enhanced production of IL2 and interferon
b) Reduces postoperative infection rates of
immunocompromised patients
2. Thymopoietin
a) Stimulates differentiation of T-cells while
inhibiting differentiation of B-cells
b) Increased IL2 and IL2 receptor expression
c) Increased size of T-cell pool
d) Increased NK-cell activity.
3. Thymulin (Serum thymic factor)
a) Increases T-cell populations probably via
stimulation of IL1
b) Production stimulated by PRL & GH
D. AIDS
1. Thymic peptides have been used to enhance the
immune system of HIV infected individuals.