THE EFFECT OF STEROIDS ON THE CIRCULATING LYMPHOCYTE POPULATION V. EFFECT OF PREDNISOLONE TREATMENT ON CELL SIZE AND LIFE SPAN OF THE THORACIC DUCT LYMPHOCYTE POPULATION IN NORMAL AND NEONATALLY THYMECTOMIZED RATS. - A RADIOISOTOPE STUDY

Abstract

Using 3H-TdR isotope labelling in vivo, the effect
of a high corticosteroid dose was correlated to cell
size and life span of thoracic duct lymphocytes in
rats.
The lymphocytopenia in thoracic duct lymph during
the involution phase (3 hrs after treatment)
was a marked depletion of small lymphocytes, fol lowed
by a restitution to pretreatment cell levels
within one day. The original lymphocyte population
had a higher per cent of labelled small lymphocytes
(50%) in comparison to the returning population
which contained fewer (35 %) small labelled cells.
Label index (i.e. labelled cells of a certain cell size
in percent of total cell number) was unchanged for
all cell sizes during both involution and restitution
phases.
This unchanged label index profile as well as an earlier
described unchanged cell size distribution support
the hypothesis of lymphocyte trapping and.
redistribution as a major effect of a single prednisolone
dose. The decrease of labelled small lymphocytes
in the returning cell population can, however,
also agree with a minor lymphocytolytic effect on
circulating small lymphocytes.
Our data do not support the hypothesis of two different
lymphocyte populations with different life
span. Neither could a redistribution of lymphocytes
be found in any lymphoid tissue compartment or in
femur bone marrow, during the involution phase after
corticosteroid treatment.·