de-Miranda-Santos I K, Campos-Neto A
Departamento de Microbiologia, Imunologia e Parasitologia, Faculdade de Medicina de Ribeirão Preto, Brasil.
Braz J Med Biol Res. 1995 May;28(5):585-9.
Immunoglobulin Fc receptors (FcRs), present in Trypanosomatidae pathogenic for mammals, may be a mechanism by which these parasites escape the host immune response. We studied the possible role of these receptors in evasion by the alternative complement pathway. Promastigotes of Leishmania amazonensis and trypsinized trypomastigotes of Trypanosoma cruzi treated with heat-aggregated normal gamma globulin and then incubated with fresh normal guinea pig serum were shown to be more resistant to lysis. When compared to log phase Leishmania promastigotes, this resistance was at least 4.5-fold greater in parasites harvested in the stationary growth phase. EDTA and EGTA plus MgCl2 inhibited the cytotoxic effect of serum, suggesting the participation of the alternative complement pathway. The distribution of FcRs among genera of Trypanosomatidae that are pathogenic, infective or noninfective for mammals and their affinity for mammalian and fowl immunoglobulin were also examined. These receptors are present only in species infective or pathogenic for mammals, a finding that suggests that this structure is essential for the establishment of infection but is not necessarily a virulence factor. Furthermore, the ligand specificity is limited to the immunoglobulin of mammalian but not of fowl origin.
免疫球蛋白Fc受体（FcRs）存在于对哺乳动物致病的锥虫科中，可能是这些寄生虫逃避宿主免疫反应的一种机制。我们研究了这些受体在通过替代补体途径逃避免疫方面可能发挥的作用。用热聚集的正常γ球蛋白处理亚马逊利什曼原虫的前鞭毛体和经胰蛋白酶处理的克氏锥虫的锥鞭毛体，然后与新鲜的正常豚鼠血清孵育，结果显示它们对裂解更具抗性。与对数期利什曼原虫前鞭毛体相比，处于稳定生长期收获的寄生虫的这种抗性至少高4.5倍。EDTA和EGTA加MgCl2抑制了血清的细胞毒性作用，表明替代补体途径参与其中。还研究了FcRs在对哺乳动物致病、感染或不感染的锥虫科各属中的分布及其对哺乳动物和禽类免疫球蛋白的亲和力。这些受体仅存在于对哺乳动物有感染性或致病性的物种中，这一发现表明这种结构对于感染的建立至关重要，但不一定是毒力因子。此外，配体特异性仅限于哺乳动物来源的免疫球蛋白，而不包括禽类来源的免疫球蛋白。
