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Introduction
Currently, many biological response
modifiers (BRM) have been identified. Examples are interleukins and
cytokines. Also, the thymus plays an important role in the overall
immunomodulation. One could say, that the thymus is the ?gbrain?h of the
immune system. In 1560, Andrea Vesalus made a first description of the thymus
but it took almost four centuries until in 1936, Hammar suspected that the
thymus plays an important role in the immune system after birth. Today, the
thymus is considered to have a key function in the development and function
of the immune system and the biological defence mechanisms against cancer and
chronically infected cells.
Thymic tissue is responsible for selected transformation of
precursor cells into different T-cells, i.e. helper (CD4+) T-lymphocytes,
which aid in the differentiation of other lymphocytes, killer cells (NK
cells) cytotoxic cells and suppressor (CD8+) Tlymphocytes (1-3). Having been
released into the blood stream, intestinal and peripheral tissues, the
lymphocytes are characterized by well-defined antigens or activation markers
on their surface. Their activities are extra thymic.
The thymus is directly innervated and its role in the interaction between the
immune system and the neuroendocrinal systems can therefore be understood. In
newborn mice, thymectomy causes a significant change and decrease of
lymphatic tissue and a hypofunction of the Reticulo-Endothelial System (RES).
In addition, the maturation of T-dependent lymphocytes is severely hampered,
or even made impossible. The thymus produces a variety of substances,
including thymus-specific enzymes, - proteins, -peptides and -steroids, which
all have both central and peripheral activities. Thymus peptides have a
molecular weight of about 300 - 100,000 Dalton. Up to now, some peptide
fractions have been isolated and identified, mainly from the thymus glands of
young calves, or foetus.
Thymus peptides also play an important role in the development, maturation,
differentiation and activation of T-lymphocytes. In addition, thymus peptides
enhance proliferation of precursors of lymphoid cells in bone marrow, and
their maturation into Tlymphocytes (1-3).
Thymus and its
effects on haematopoietic factors...
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