Effect of <i>Trichinella spiralis</i> Infection on Delayed Hypersensitivity to Heterologous Antigens

Abstract

Studies were initiated to determine the effects of the different phases of the nematode life cycle on the delayed-type hypersensitivity (DTH) capabilities of the host. Mice were injected intraperitoneally with 4 × 10⁶ viable or heat-killed BCG at 0, 3, 7, 14 and 28 days after oral infection with 200 Trichinella spiralis larvae. Groups were tested for DTH 28 days after BCG inoculation by the footpad swelling assay. Infection with T. spiralis was found to suppress the response in mice administered viable BCG 0 or 3 days later. Mice injected with viable bacteria 7 days after T. spiralis regained the ability to develop in vivo DTH reactions against old tuberculin. Groups administered viable BCG 14 and 28 days after nematode infection yielded potentiated DTH responses, when compared with control mice. Animals infected with T. spiralis and later injected with heat-killed BCG required a longer interval to develop specific immunopotentiation. Maximum immunopotentiation seemed to be related to the presence of larvae in muscle tissue (28 days). These findings suggest that the effect of T. spiralis on the immune capabilities of the host is dependent on the different anatomical locations of the parasite.

Potentiation of MIF Production by Lymphocytes of <i>Trichinella spirali</i><i>s</i>-lnfected Mice

“…These levels were comparable to those shown previ ously with this assay [16] and served as a positive con trol group for this system. Of the mice administered heat-killed BCG, only 1 displayed a titer greater than 8; and the mean reciprocal titer of 3 for this group confirms the low level of DTH footpad swelling re sponsiveness reported previously [1,12], No T. spira-/r.v-infected animals developed any detectable MIF upon challenge with OT, suggesting the absence of a cross-reaction between these two agents. Prior infec tion of mice with Trichinella enabled them to produce significantly elevated titers of MIF to heat-killed BCG (p < 0.003), at levels comparable to those seen in the viable BCG and T. spiralis-v\db\e BCG-immunized animals.…”

“…If the only ef fector cell operating is a non-specifically-activated macrophage, then MIF levels would not necessarily be elevated. Lymphokine titers observed in parasiteand BCG-infected mice paralleled previously report ed footpad swelling reactivity [1,12], Immunization with only heat-killed BCG elicited no specific MIF upon OT challenge, but a prior Trichinella infection resulted in titers equivalent to those seen in viable BCG-sensitized animals. Because no cross-reactivity was observed in T. spiralis-infected mice to OT, one can presume that the MIF produced in the dually in fected animals was due to the enhanced function of a specifically sensitized lymphocyte.…”

“…This included increased protection from bacterial and parasitic infections and tumors [1,3,4,8,[10][11][12][13][14]. Peritoneal macrophages have been shown to be activated and increased in a number of these animals [20,21] and have been implicated as non-specific mediators of the observed phenomena [15,20).…”

“…The methods of harvesting T. spiralis larvae and bacteria and infecting mice have been described pre viously [1,6). Each animal was orally administered 200 washed, viable larvae.…”

Sequential Mesenteric Lymph Node Histological Response following <i>Trichinella spiralis</i> Infection

“…A number of reports have attempted to delineate the causal relationships between different phases of the helminthic life cycle with observed humoral and cel lular immunosuppression [1,[3][4][5]10] and cell-mediat ed potentiation [1,2,11,13]. Histologic investigations have sought to correlate changes in the microscopic appearance of lymphoid tissue with the observed ef fects on cellular immunity.…”