Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)
KEY WORDS: review, protective immunity, effector mechanism, intestinal helminths, worm expulsion, mucosal cells and cell products, mucus trapping, immune depression of worm metabolism. It is known that gastrointestinal immunology and the functions of the gut associated lymphoid tissues constitute a special field of interest within the general term of immunology, with respect to the great variety of implications of that system of defense in clinical gastroenterology. From parasitological point of view the gastrointestinal mucosa presents a large surface through which many internal parasites invade their vertebrate hosts, and which provides a habitat for many internal parasites causing considerable loss to animal production and human health. The lack of knowledge of gastrointestinal immunophysiology had hindered for a long time also the analysis of immunity against intestinal worms. In recent years, however, significant advances have occurred in the understanding of mucosal immunology. For details most valuable textbooks, such as of WAKE LIN (1984), OUTTERIDGE (1985h and HEYWORTH and JONES (19881 can be consulted. The immune expulsion of intestinal worms is associated with an inflammatory reaction of the intestinal mucosa. It is the major goal of the related studies to achieve a fair understanding of the processes leading to the development of structural and functional alterations of the Intestine, and of the effect of these changes on worm physiology and survival. COMPONENTS OPERATING IN THE IMMUNE RESPONSE It is known that the immune and inflammatory reactions operating in protective responses against intestinal worms involve a great variety of cellular and humoral components . The diagrammatic and - of course - simplified representation taken from the book "Immunity to Parasites" (1984) by WAKELIN presents an idea of the complexity of the interplay between macrophages, lymphocytes, myeloid cells, cytokines and antibodies in the sequence of events induced by worm antigens (Fig. 1). 1) Lymphocytes, macrophages The involvement of T lymphocytes in the host' s response to helminth infection has long been the subject of much interest and research. It has been shown that in the initial phase of induction of the immune response macrophages activated by parasite antigens produce a soluble factor, interleukin 1 (IL-1) which stimulates T cells to express receptors for inter- leukin 2 (IL -?.) . Primed T cells release 11-2 which mediates clonal expansion of wormspecific helper T cells largely in the mesenteric lymph nodes. T cells release also IL3. This lymphokine has a boosting effect on T cell proliferation, and has a mast cell growth stimulating potential. A further lymphokine produced by primed T cells is interferon f (IFN- X , IF- y ) which Is thought to have a regulatory role of interleukin production (NATHAN et al. 1984; GRENCIS, RIEDLINGER and WAKELIN 19871. There Is no evidence to suggest that interferon can directly interfere with worm physiology, however, it might have a role in the priming of leukocytes to generate free oxygen radicals, components which may mediate worm expulsion either indirectly by altering intestinal environment, or by damaging worms directly (SMITH and BRYANT 1986L The T and B cell cooperation Is known to
