The phospholipase B content of the intestines of rats infected with varied larvae doses of Nippostrongylus brasiliensis

Effects of Plasmodium berghei (Apicomplexa) on Nippostrongylus brasiliensis (Nematoda) infection in the mouse, Mus musculus

Ova and free oxygen radical production and relative peripheral eosinophilia during single and concurrent infections in mice with P. berghei and N. brasiliensis were investigated. Prolonged helminth patent periods indicate that Nippostrongylus self-cure in concurrently infected mice was suppressed. Differential white blood cell determinations showed that the relative number of peripheral blood eosinophils steadily increased (P < or = 0.05) during a Nippostrongylus infection when compared to noninfected controls. Eosinophil levels in mice singly infected with P. berghei or concurrently infected with both parasites did not differ significantly from those of controls suggesting a suppression by Plasmodium of Nippostrongylus-induced eosinophilia. Generation of intestinal free oxygen radicals was indirectly assessed using the Thiobarbituric Acid Assay to measure malondialdehyde (MDA). Intestinal MDA levels were significantly elevated (P < or = 0.05) during single Plasmodium infections as well as concurrent infections while there was no change in MDA production during single Nippostrongylus infections. These results suggest suppression by Plasmodium of the immune response to Nippostrongylus, allowing prolonged patent periods. They also suggest that eosinophils play a role in self-cure while free oxygen radicals do not.

Light and electron microscopic demonstration of phospholipase B activity in the mouse eosinophil

Phospholipase B (EC 3.1.1.5) which hydrolyzes phospholipids in the alpha and beta positions was demonstrated in murine leukocytes using light and electron microscopic histochemical techniques. Leukocytes (neutrophils, lymphocytes, macrophages, eosinophils) were harvested from peritoneal exudates of mice. Cells were fixed in 4% calcium-formol fixative for 10 min at 4 degrees C for light microscopy and 30 min at room temperature for electron microscopy, after which they were incubated at 37 degrees C in medium at pH 6.6 containing 2 microM lysolecithin and CaCl2. The fatty acids released during the hydrolytic reaction were trapped as a calcium precipitate and were converted to a cobalt precipitate for light microscopy by treatment with cobalt acetate or to a lead precipitate for electron microscopy by treatment with lead nitrate. The reaction products were observed to be present in eosinophils and absent in neutrophils, lymphocytes and macrophages. It is concluded that the eosinophilic leukocyte is the carrier cell for phospholipase B in inflammatory reactions.

Effect of anti-thymocyte serum on the eosinophil and lysophospholipase responses in mice infected with Trichinella spiralis

Anti-thymocyte serum (ATS) was administered to CD-1 mice infected with 100 Trichinella spiralis larvae and its effects on intestinal lysophospholipase (EC 3.1.1.5) activity, peripheral blood lymphocytes and bone marrow, peripheral blood and intestinal eosinophilia were assayed in the same experimental animal. The ATS caused a significant suppression of both the tissue lysophospholipase response and eosinophilia, in all three compartments, when compared to the values found in infected mice that were either treated with normal rabbit serum (NRS) or untreated. The suppressed eosinophil response and reduced lysophospholipase activity demonstrated a close temporal relation throughout the experiment. These findings support the hypothesis that helminth parasite-induced eosinophilia is the cause of increased lysophospholipase activity present in parasitized tissue and that the responses are thymus cell dependent.

Helminth-induced intestinal inflammation

Gastrointestinal inflammation is a prominent feature of protective reactions in animals immune against helminths. Infiltration into the inflamed mucosa of various cells and their subsequent activation result in the elaboration of an array of pharmacologically and biologically active substances. The release of mediators is also associated with alterations in the epithelial layer. Furthermore, increased smooth muscle reactivity and enhanced secretory function of the mucosal tissue contribute to the development of an unfavourable environment and lead to worm expulsion. Mediators elaborated from inflammatory cells, whether associated with cell granules (i.e., preformed) or de novo-generated from membrane phospholipids, possess a number of potent vasoactive and spasmogenic properties which may contribute to events leading to worm elimination. The lipoxygenase metabolites of arachidonic acid (leukotrienes) derived from cell membranes probably contribute to the state of intestinal hypersensitivity against helminths. The measurement of elevated levels of these lipid mediators following worm challenge of immune, but not control, rats suggests that leukotrienes may play a role in amplifying and augmenting the inflammatory process associated with worm expulsion.