الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The lymphoid tissues of the gastrointestinal tract are an
important component of the immune defense mechanism in the body.
The cells of the immune system, principally lymphocytes, are
disseminated throughout the body either as isolated cells, or as
localized aggregations particularly in the gastrointestinal tract and
lymphoid organs (Wheater et al., 1987). In addition to the thymus
which involutes in adult life, lymphoid tissues are mostly located in
the spleen, lymph nodes, and in the walls of the intestine. Previous
studies have focused on the morphology and the architecture of the
spleen (Pobst, 1988), lymph nodes (Weiss, 1988) and colon (Cormack,
1987), in adult mammals. Also, the distribution of thymus-dependent
and thymus-independent areas in such organs, in adult mammals, has
been previously investigated (Gutman and Weissman, 1972; Goldschneider
and McGregor, 1973). However. the study of the early
postnatal growth of the lymphoid areas of these organs, as well as the
distribution of T and B lymphocytes has received little attention.
Therefor~,-the aim of the present work is to study the postnatal __,
development of the lymphoid tissues in the white pulp of the spleen,
the cortex of mesenteric lymph nodes and the wall of the cecum in rat. The distribution of the T- and B-cell areas in the white pulp of the
spleen and the cortex of the mesenteric lymph nodes of rat will be
studied as well.
There has been considerable interest in the pharmacologic use of
corticosteroids administered on alternate-days rather than in daily
divided doses, in an effort to reduce the side effects which occur with
chronic treatment (Reichling and Kligman, 1961). In most cases, the
therapeutic effectiveness of the alternate-day therapy program was
nearly similar to that with daily dosage schedules (Soyka and Saxena,
1965: Soyka, 1967). The alternate-day corticosteroid regimen
succeeded to minimize or prevent manifestations of Cushing’s
syndrome traditionally associated with long-term steroid therapy
(Soyka and Saxena, 1965; Soyka, 1967: Sadeghi-Nejad and Senior,
1969). In addition, steroid therapy given on alternate-day program
showed that the normal growth pattern. estimated by recording
heights and weights, in infants and older children is not suppressed
(Bacon and Spencer, 1973: Dluhy et a!.. 1973: McEnery et a!. 1973:
Preece, 1976: Byron et a!., 1983). Previous studies reported that
corticosteroids, administered on daily divided dosage schedules, cause
destruction of lymphoid tissues in certain animal species. including
rats (Everett and Tyler. 1967: Esteban, 1968). On the other hand. the
study of the immunosuppressive changes as a result of alternate-day
steroid therapy in the young and adult rats has not been investigated.
Also. the study of the long-term consequences of such therapy in the immunologically immature rats has not been determined. Therefore,
the aim of the present work is to study the effects of alternate-day
corticosteroid therapy on the immune system of the postnatal rat and
to detect the possible reversibility of such effects.