Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis. II. Changes in cell numbers following infection of thymectomised and adoptively or passively immunised guinea-pigs

Do basophils play a role in immunity against parasites?

The link between parasites and eosinophilia has been known for more than a century, although the role of eosinophils in host protection is still an open issue. Much less appreciated, however, is the concurrent systemic induction of a related cell type, the basophil, in parasitized hosts. To date, little is known about the role of basophils in immunity against parasites, but recent evidence points to a possible crucial role in the initiation of T-helper type 2 responses in the host. In this article, we review the current understanding of parasitic infections and basophils and discuss their putative role in immunity.

Eosinophils and mast cell homogeneity of the guinea pig eyelid skin, conjunctiva, and ileum

Mast cell heterogeneity has been described on the basis of differential staining reactions, light microscopic morphology, anatomic location, degranulation after polyamines, biochemical contents, growth requirements, and reactions to lymphokines. We have demonstrated typical "connective-tissue mast cells" by using anatomic criteria, histological staining reactions, electron microscopy, and reaction to compound 48/80 in the guinea pig conjunctiva, eyelid skin, and ileum. A second, much larger population of cells in the ileal mucosa and the conjunctiva, and rarely in the eyelid skin stained reddish-blue with acid toluidine blue in tissue fixed in ethanol-acetate-lead subacetate (BLA) and with alkaline Giemsa in formaldehyde-fixed tissue, did not stain with ethanolic or acid toluidine blue in formaldehyde-fixed tissue or with alkaline Giemsa in BLA-fixed tissue, and did not degranulate after 48/80 treatment. These are features of the rat intestinal "mucosal mast cells"; however, ultrastructural and light microscopic studies with the orcein Giemsa stain demonstrated these cells in the guinea pig to be eosinophils. Tissue culture, biochemical, and immunological studies indicate the existence of a second type of mast cell (bone-marrow-derived mast cell), ultrastructurally almost indistinguishable from the connective tissue mast cell. Our studies demonstrate only one mast cell type in the guinea pig and support the contention that other forms of mast cells are immature forms or variants of the connective-tissue mast cell.

Cell-mediated damage to helminths

Although it is difficult to draw any sweeping conclusions that would be applicable to all helminth infections, the main features that are emphasized in this review may be summarized briefly. Pathogenic helminths, although extremely diverse in structure and behaviour, have one common feature, namely that they present to the host's defenses large, non-phagocytosable surfaces. Because of this, they are susceptible to a range of effector mechanisms differing either quantitatively or qualitatively from those that are active against other parasites or against normal or abnormal host cells. As an extreme example, the various types of cytotoxic lymphocyte, with one interesting exception, are inactive against helminths. Instead, helminth infections are characterized by high IgE responses and increased numbers of circulating eosinophils. Such eosinophils are activated, and show a marked capacity to kill a variety of target helminths in vitro. Further activation may occur in response to mast cell mediators released as a result of IgE-dependent degranulation; and IgE, as well as IgG and complement, can mediate eosinophil attachment and killing. It may therefore be suggested that the eosinophil/IgE/mast cell axis represents a powerful host defense against helminth infections. IgE can also mediate macrophage-dependent killing of several helminths, a process which involves a functional change in the macrophage, resembling activation. Although eosinophil-mediated and IgE-dependent macrophage-mediated effects are particularly potent, other effector cells are not excluded: in certain circumstances, neutrophils and conventionally activated macrophages may be equally or more effective. Neutrophils appear to act solely by oxidative killing mechanisms, whereas degranulation and the release of toxic granule contents is equally or more important in eosinophil-mediated damage. Different stages of different helminths vary in their degree of susceptibility to different mechanisms. Eosinophils appear to be somewhat less active than neutrophils against ensheathed nematodes, whereas trematodes and exsheathed nematodes are highly susceptible to eosinophil attack. In many experimental helminth infections, studies in vivo suggest a role for antibody-dependent cell-mediated immune effector mechanisms. The identity of the effector cell is difficult to establish because of a lack of techniques for specific manipulation of individual cell types, but histological studies frequently point to a strong eosinophil or macrophage involvement. The development and analysis of in vitro assays allows the study of immune effector mechanisms in man.(ABSTRACT TRUNCATED AT 400 WORDS)

The pathogenesis of a single challenge dose of Haemonchus contortus in lambs under six months of age

The pathogenesis of H. contortus infection in lambs under 6 months of age challenged orally with 10,000 third stage infective larvae is described. The development of the parasite and its relationship to haematological and pathological changes are discussed, with particular reference to specific cellular mobilizations, and detailed descriptions are given of the haematology and parasitology, gross pathology and histopathology at 4, 7, 12, 18, 22 and 35 days after infection. Dramatic changes had developed by day 12.