Central European Journal of Immunology 2011; 36(3)
188
Review paper
Correspondence: Prof. Wanda Stankiewicz, Military Institute of Hygiene and Epidemiology, Department of Microwave Safety, Kozielska 4,
01-163 Warszawa, e-mail: wanda.stankiewicz@gmail.com
Introduction
The thymus is the first completely developed organ in
our individual life. Its activity, the most vigorous in fetal
and neonatal period, is continued with gradually decreased
intensities till the end of our life. The thymus is the center
of development of immunocompetence of immigrant bone
marrow-derived lymphocytes which progressively differ-
entiate into separate T-lymphocyte subclasses. Intrathymic
environment composed of the network of thymic epithelial
cells (TEC) presents to incoming cells the template of self
histocompatibility antigens of the HLA-first and the HLA-
second class. They are ligands for recombinantly develop-
ing T cell receptors (TCR) which together with co-recog-
nizing structures (CD4 or CD8) create the mechanisms of
immune recognition. The T lymphocytes with the shape of
TCR able to recognize the self histocompatibility antigens
(HLA-restriction), thus able to discriminate between the
correctness of self or incorrectness of self deformed by
influence of foreign elements (including infective antigens),
are positively verified and selected by the supportive influ-
ence of thymic epithelial cells. TEC are producers of some
cytokines, growth factors (e.g. IL-1, IL-7, oxytocine,
enkephalins) and specific polypeptides collectively
described as a “thymic hormones”. These substances are
highly sensitive for enzymatic proteolysis and their life-
span in circulation is very short. Their repeated impulses
delivered by the active thymus are indispensable for com-
pletion and finalization of the process of maturation of T
lymphocytes which takes about two weeks in human [1].
Leaving the thymus, newly matured T lymphocytes repre-
senting the all known classes of the population (T-inducer-
helper, T-cytotoxic, T-regulatory cells), reach the peripher-
al lymphoid system as a recent thymic emigrants (RTE).
This is the physiologic way or replenishment of cellular
resources of immune system exploited by its numerous
defensive, regenerative, tolerant and regulatory functions.
The thymic supplementation of immune system with the
new cellular cohorts to replace the exploited resources is
a whole-life process, the most intensive at the perinatal peri-
od. Nevertheless, even in the adult and elderly individuals
the thymic lymphopoietic and endocrine functions are main-
tained, as indicated by the appearance of the new RTE cells
in the circulation [2-4]. In consequence, the proper activi-
ty of the thymus leads to the functional efficiency of
immune system in the full scope of its activities and the
The thymus in neuro-endocrine-immune
network
MAREK P. DĄBROWSKI , MACIEJ I. DĄBROWSKI, WANDA STANKIEWICZ
Military Institute of Hygiene and Epidemiology, Department of Microwave Safety, Warsaw, Poland
Abstract
On the grounds of concise review of literature comprising the most important findings achieved by
different investigators during over fifty years of intensive research, authors describe the present state-
of-art knowledge on the immunoregulatory role of thymus. Being responsible for creation of immune
competence of T lymphocytes, the thymus is able to control immune functions also by regulation of immu-
nity indirectly by neurohormonal mechanisms. They comprise both synergistic (e.g. growth hormone,
prolactin, enkephalins, thyroid hormones) and antagonistic (e.g. adrenal and sex hormones) connec-
tions between the thymus and neurohormonal system. This way, remaining active for the whole life of
the organism, providing both cellular and hormonal influences, the thymus integrates and maintains the
homeostatic tasks of neuro-endocrine-immune network related to its metabolic, procreative, regenera-
tive, tolerogenic and defensive functions.
Key words: the thymus and neurohormonal regulation of immunity.
(Centr Eur J Immunol 2011; 36 (3): 188-192)
