Since the interest on the thymus as an organ essential for the
development of immunological capacity was renewed more than ten years
ago, the search for a better understanding of the mecha- nisms
underlying its functions has not come to an end. Although the first
observations suggesting a link between the thymus and immunocompetence
related to certain clinical disorders in man such as thymoma or Swiss
type of agammaglobulinemia, the bulk of evidence demonstrating the role
of this lymphoepithelial organ in immune reactivity originates from
experimental work as ini- tiated by Dr. MILLER and Dr. Goon's group. The
full significance of the thymic system is now beginning to unfold. The
basic question to be answered by the many investigators in the field is
no longer whether the thymus does in fact play the role of an
immunologically important organ but rather how it acts. In addition we
need to know in what period(s) of ontogenesis is a proper development of
the thymus a prerequisit for the buildup of an efficient peripheral
lymphoreticular system throughout the organism. Perinatal thymectomy
proved to be a valuable experimental approach to gain a better insight
into thymic functions. At first it looked as if this measure, in most of
the species tested, would largely depress or abolish all immune
reactions of the animal and lead to an inescapable wasting syndrome
within a few months.