BALB/c mice have been an exceptional susceptibility to Leishmania tropica infection such that cutaneous lesions grow without restraint in all cases leading to fatal metastasis and visceralization in normal and x-irradiated, bone-marrow reconstituted (XBM) animals. Adult thymectomized, x-irradiated, bone marrow-reconstituted (ATxXBM) BALB/c mice, however, show pronounced retardation of lesion growth leading to some survival and even cures. A similar trend was also found in moderately susceptible (BALB/c X C57BL/6)F1 mice, in contrast with the "resistant" CBA strain, in which, as previously known, ATxXBM animals showed impairment of normal, spontaneous self-healing. These convere effects are paralleled by respective leishmania-specific delayed-type hypersensitivity (DTH) reactivities, prior thymectomy leading to diminution in CBA and augmentation in BALB/c and (BALB/c X C57BL/6)F1. Anti-leishmanial DTH responses, amplfiable by cyclophosphamide pretreatment, can be detected in BALB/c mice within 10 d of infection with 2 X 10(7) promastigotes, but becomes near-totally suppressed by day 25-35. No such suppressin is found in CBA, C57BL/6, or (BALB/c X C57BL/6)F1 mice together with varying degrees of immune control of lesion development or regression. Suppression of DTH in BALB/c mice is leishmania specific and does not extent to 2,4-dinitrofluorobenzene (DNFB) or sheep erythrocytes specificities. Spleen cells from suppressed L. tropica-infected mice when transferred to normal BALB/c mice impaired the induction of DTH to leishmanial antigen. This property resided in the T cell-enriched fraction and not in the T cell-depleted fraction. It is concluded that a major component of the striking inability of BALB/c mice to control L. tropica infection involves profound impairment of a potentially curative cell-mediated immune response by suppressor T cell generation. The possibility is discussed that this may be secondary to rapid amastigote (antigen) accumulation in macrophages expressing the primary genetic "defect."
Immunological regulation of experimental cutaneous leishmaniasis. III. Nature and significance of specific suppression of cell-mediated immunity in mice highly susceptible to Leishmania tropica.
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J G Howard, C Hale, F Y Liew; Immunological regulation of experimental cutaneous leishmaniasis. III. Nature and significance of specific suppression of cell-mediated immunity in mice highly susceptible to Leishmania tropica.. J Exp Med 1 September 1980; 152 (3): 594–607. doi: https://doi.org/10.1084/jem.152.3.594
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