Immunosuppressive potency and in-vitro activity of antilymphocyte globulin

Monocyte-Derived Suppressor Cells in Transplantation

Myeloid-derived suppressor cells (MDSC) are cells of myeloid origin with enhanced suppressive function. They are negative regulators of the immune responses and comprise a heterogeneous mixture of immunosuppressive cells of monocytic (M-MDSC) and granulocytic (G-MDSC) origin. A more recent nomenclature proposes the term "suppressive monocyte derived cells" (suppressive MCs) to define CSF1/CSF2-dependent mouse suppressor cells that develop from common monocyte progenitors (cMoPs) after birth. Here, we review the literature about monocytic-derived cells with demonstrated suppressor function in vitro and in vivo within the context of solid organ transplantation.

Anti-idiotypic antibodies from highly sensitized patients stimulate B cells to produce anti-HLA antibodies

BACKGROUND

Sustained allosensitization increases waiting time for transplantation and increases the risk of rejection. The purpose of this study is to examine the effect of anti-idiotypic antibodies on B-cell responses and to define their role in alloantibody production.

METHODS

The Immunoglobulin G (IgG) fraction, or the sera of 19 highly sensitized (HS) patients was absorbed to remove anticlass I antibody and was incubated with B cells. The culture supernatant was assayed for antihistocompatibility leukocyte antigen (HLA) antibody and tested for reactivity against a panel of normal lymphocytes. Similar studies were performed in 5 of the 19 patients who had a fall in alloantibody levels.

RESULTS

The IgG (HS) fraction induced anti-HLA antibody from normal and autologous B cells in all 19 HS patients studied. The reactivity to HLA antigens in the culture supernatant was similar to the sera for each patient studied. The in vitro generated anti-HLA antibody bound to the IgG fraction used to stimulate the B cells. The in vitro production of anti-HLA antibodies was absent in the serum of all five patients who became nonsensitized.

CONCLUSIONS

All patients who have high levels of alloantibody have anti-idiotypic antibodies in their sera that stimulate B cells to produce anti-HLA class I antibody similar in reactivity to that of their own sera. In the patients who have nondetectable alloantibodies in their sera, the stimulating anti-idiotypes are not measurable. Anti-idiotypic antibodies may act as a vaccine and cause sustained levels of alloantibody production.

Effect of immunosuppression on the size and metastasis of amoebic liver abscesses in hamsters

The effect of T-cell depletion on experimental hepatic amoebiasis in hamsters was investigated. Thymectomized and anti-T-cell (ATS) treated animals as well as sham-operated and unoperated controls were inoculated intrahepatically, following laparotomy, at 7 weeks of age with 1 x 10(5) axenic trophozoites of Entamoeba histolytica. In neonatally thymectomized hamsters the mean weight of the liver abscess 10 days post-inoculation was significantly greater than in neonatally sham-operated or unoperated controls, but there was no significant difference between these groups of animals in the size of metastatic foci to other organs. On the other hand, a combination of neonatal thymectomy and ATS treatment enhanced both the size of the primary abscess in the liver and the size of metastases to other sites. Adult thymectomy did not have a significant effect either on the size of the primary abscess or on metastatic dissemination of amoebae from the liver. Treatment of hamsters with ATS shortly before or after intrahepatic challenge increased significantly the size of the abscess, but similar treatment 2-3 weeks prior to challenge had no effect. These observations suggest that thymus-dependent cell-mediated immunity plays an important role in the host response to E. histolytica infection.

Surface properties of cells isolated from non-metastasizing and metastasizing hamster lymphosarcomas

Present evidence suggests that the cell surface has an important role in metastasis. To examine this idea further, the surface properties of single cells isolated from the primary growths of a liver-metastasizing (ML) and a non-metastasizing (NML) lymphosarcoma were compared for adhesion to cell monolayers, cytopherometry, isoelectric focusing, adhesion to immobilized lectins and surface labelling with lactoperoxidase-catalysed radioiodination. It was found that the ML cells had increased adhesion to 3 out of 4 of the monolayers studies; a lower overall surface charge but greater peripheral concentrations of charge; and increased surface expression of the fucose moiety. No consistent difference between the two cell types was detected in the electrophoretic pattern of the labelled surface proteins. These findings are discussed in the light of present knowledge of the cell surface, and it is concluded that the significance of any of the observed changes in relation to metastasis has yet to be established.

The L.A.I. microtest: a rapid and sensitive precedure for the demonstration of cell-mediated immunity in vitro

A new microtest for cell-mediated immunity is described, which is based on the elaboration of a diffusible factor from sensitized lymphocytes following contact with specific antigen. The factor inhibits the adherence of neighbouring leucocytes to plastic surfaces. Production of the factor is ablated by pretreatment of lymphocytes with Theta-antiserum. It is suggested that the factor may be a new lymphokine, leucocyte adherence inhibition factor (LAIF).