ANTIBODY-INDUCED MOVEMENT OF MEMBRANE COMPONENTS OF LEISHMANIA ENRIETTII

Abstract

Protozoal parasites of the genus Leishmania have a unit trilaminar surface membrane (1). Such membranes in mammalian cells are considered to be lipid bilayers in which the integrated membrane proteins are capable of translational diffusion (2). Movement of surface membrane components of mammalian cells into discrete aggregates or a single aggregate, a "cap", has been observed after reaction with ligands such as specific antibody and Concanavalin A (3-8). These aggregates m a y subsequently be endocytosed or shed. Such changes in membrane components m a y constitute the initial step in important phenomena such as antigenic modulation, lymphocyte activation, and immunological tolerance (3-5, 8).Here we describe the effects of antibodies on surface membrane antigens of the amasfigote and promastigote forms (9) of Leishmania enriettii. These include aggregation and distinctive forms of capping with at least temporary loss of antigens from the surface of the parasite. Materials and MethodsParasites.--Viable amastigotes were obtained from infected macrophages by excision and maceration of lesions produced in guinea pigs by intradermal inoculation of L. enriettii 3-6 wk previously (10). Parasites were recovered by centrifugation, washed, and resuspended in Dulbecco's modification of Eagle's medium (11), supplemented with 10% fetal calf serum. Promastigotes were cultured at room temperature in the same medium supplemented with 5% fetal calf serum and 5% of a solution of human hemoglobin (growth medium).Antibodies to Leishmania.--Guinea pigs were infected intradermally with L. enriettii and sera were obtained either during the course of disease (3-6 wk after infection) or after challenge of immune animals with healed lesions. An indirect fluorescent antibody test on formalin-fixed parasites showed antibody titers from 1:54 to 1 : 1,024 in these sera.3,z-globulins isolated from immune sera by DEAE-cellulose chromatography (12) gave similar results to those described for unfractionated sera in immunofluorescence of viable parasites. Immune sera were heated to 56°C for 30 min before use in immunofluorescence.

Surface properties related to concanavalin A-induced agglutination. A comparative study of several Entamoeba strains.

“…15, E. moshkovsku; Fig. 16, HM2 axemc, Fig 17, recently in both amastigote and promastigote forms of Leishmania (34). The polar redistribution of Con A receptors (35), and of E. histolytica membrane antigens (36, Trissl and CalderSn, in preparation), is followed either by the rapid internalization or shedding of the surface complexes from the parasite.…”

Trypanosoma brucei gambiense and T. b. rhodesiense: Concanavalin A Binding to the Membrane and Flagellar Pocket of Bloodstream and Procyclic Forms1

“…If trypanosome surface glycoproteins recycle, they probably pass through the flagellar pocket since this is the only place where endocytosis occurs in these parasites (1 9, 26). Antibody sometimes induces capping of trypanosomatid antigens at the anterior end of the flagellum (3 l), but caps usually move to the flagellar pocket or cell posterior (2,3,6,7,12,30,31). Endocytosis of caps occurs in the pocket (3).…”

“…Endocytosis of caps occurs in the pocket (3). With one exception (12), capping has not been observed at 0" C or when univalent Fab fragments or bivalent antibody were used in the absence of an immunoglobulin cross-linking reagent (2,3,6,7,12). We find that Fl-s-Con A, which is bivalent (1 3), bound to the flagellar pocket of cells maintained on ice.…”

“…Fluorescence of the flagellar pocket and flagellum appeared more intense and surface fluorescence less intense when either cell type was incubated 15 min at physiological temperature after binding lectin as described in Table I1 (Figs. [6][7][8]. No staining could be observed in controls incubated with 25 rcg/ml Fl-s-Con A and 100 mM AMM or with 25 pg/ml Fl-BSA (not shown).…”

Immune Responses in Parasitic Diseases. Part A: General Concepts

“…This ability both masks parasite antigens and presents a screen of host "self' antigens to the immune system. Antigenic depletion refers to the stripping of antigens from the surface of the parasite by a shedding mechanism, such as that observed for the tegument of S. mansoni [26], or the capping and shedding of surface antigens, such as that described for Leishmania enriettii [27]. In the latter example, antibody capping and shedding reportedly results in the insensitivity of the organism to the addition of fresh antibody and complement [21].…”