Nuclear Medicine Technology
Health Applications
and Other
Project Title: Lymphocytopoiesis and Transpiantation Immunology
16. Technical Progress in FY 1973:
(Cont'd)
Peyer's patch, and bone marrow.
RX-01-03-(d)
Lymphocyte concentration in the blood
declined continuously during ECIB.
Repletion of lymphocytes began a.
few days after cessation of ECIB and continued for the duration of the
study.
Complete recovery, however, was not achieved by 2 months after
termination of ECIB.
Changes similar to those seen in blood lymphocyte
concentration (decrease and recovery) were also observed in the thoracic
duct lymph.
The spleen, lymph nodes, thymus, and Peyer's patches showed
various degrees of lymphocyte depletion during ECIB.
Lymphocyte concentration in the bone marrow remained constant.
Within the two-month
experimental period, the thymus, lymph nodes and Peyer's patches recovered
completely while the spleen, despite showing some recovery, remained
partially depleted for the entire period.
Following cessation of ECIB,
the lymphocyte concentration in bone marrow increased, reaching a; level
above the controls by day 4.
Thereafter it returned to the level of
the mean sham control groups and appeared to remain below this level
for the entire period of the study.
During ECIB an increase in the flash
labeling index of the dividing population of lymphocytes was noticed in
the bone marrow, Peyer's patches, blood and thoracic duct lymph.
increase was most marked in the bone marrow.
The
The peak level of the
labeling index of the bone marrow was attained on day 4 following cessa-
tion of ECIB,
also peaked.
the time at which the lymphocyte concentration of bone marrow
Thymus and spleen did not show any appreciable change in
the labeling index as a result of ECIB.
An increase in labeling index
of the dividing population of lymph node lymphocytes was observed during
ECIB and sham ECIB.
The observation that ECIB-induced lymphocytopenia
initiated a stimulatory signal for increased proliferative activity of
lymphocytes in the bone marrow is new and exciting and may shed light
on one of the original objectives of ECIB, namely, and to show whether
partial depletion of lymphocytic tissues triggers proliferation within
some segment of the lymphocytic system. Whether this increased pro-
liferation is in response to increased cell destruction, or to a mechanism
that senses a decrease in size of lymphocyte pools in blood or tissues
is not known.
Earlier studies had shown that peripheral lymphocyte
depletion results in an initial, temporary depletion in the thymus
during ECIB.
The thymus is known to be repopulated by cells originating
in the bone marrow after fatal irradiation.
These facts, and the
increased proliferative activity observed in bone marrow, suggest that
there might be a feedback loop from the thymus to the marrow, stimulating
marr@M production to replete the thymus.
“Bering the preceding studies, the lymphocyte count/unit volume of
thoracic duct lymph continued to fall, reaching the lowest level a few
days after cessation of ECIB.
To study this further, thoracic ducts were
cannulated and arteriovenous shunts cstablished in calves.
One calf was
subjected to intermittent ECIB and the other received intermittent sham
(See Continuation Sheer)
[119231
RX-73