The Use of Spectral Analysis of Limiting Dilution for Investigating the Immune Response.

In this study we present a method for characterizing a spectrum of cells engaged in the humoral response by two parameters: the frequency and potential activity of antigen specific precursor cells. Spleen cells from mice immunized with ovalbumin were placed in microcultures in a limiting dilution assay. The values derived from positive cultures in an activity/cell number plot were compatible with Poisson distributions for distinct families of precursor cells displaying either positive or negative (suppressor-like) activities. Proposed limiting dilution spectral analysis combines the potentialities of the standard limiting dilution analysis with those provided by histograms of distribution according to the activity of positive cultures. This method opens new opportunities in detecting and characterizing distinct groups of limiting precursor cells.

Muramyl dipeptide-induced changes in murine splenocyte responses to concanavalin A.

The effect of muramyl dipeptide (MDP) on Con A-stimulated activation of murine spleen cells was studied. MDP was found to enhance or suppress the proliferative response of splenocytes when different concentrations of Con A were used. MDP was shown to change the IL-2 content in culture supernatants of stimulated cells and to influence IL-2-dependent proliferation of Con A-blasts. A high degree of correlation was found between the proliferation of Con A-blasts and the expression of IL-2 receptors on Con A-blasts. This correlation, however, disappeared in the presence of MDP. The effects of MDP were shown to depend on the level of initial cell activity or rather on conditions leading to a given initial activity of cells.

Target cells for immunomodulatory action of muramyl dipeptide.

Identification of the target cells for the immunomodulatory action of muramyl dipeptide (MDP) was addressed by investigation of various B-cell and T-cell lines. The lines used were: IM-9, a human lymphoblastoid B-cell line that spontaneously produces IgG; EL-4, a murine T-cell line that produces interleukin-2 (IL-2) on stimulation with phorbol myristate acetate; and CTLL-2, an IL-2-dependent murine T-cell line. MDP was shown to modulate such T-cell and B-cell functions as cell proliferation and secretion of IL-2 and IgG, respectively, in vitro. The effect of MDP in vitro was determined by both MDP dose and the control level of cell activity. The evidence obtained supports the possibility of the direct action of MDP on T and B lymphocytes.

[Leukocyte migration inhibiting factor in preparations of alpha and gamma interferons]. / Faktor, ingibiruiushchii migratsiiu leikotsitov v preparatakh al'fa- i gamma-interferona.

High titres of leukocyte migration inhibition factor (LMIF) activity were found in native and partially purified preparations of human alpha- and gamma-interferon. In the course of chemical purification of interferon up to 98% of LMIF was lost. The highest content of LMIF was in gamma-interferon preparations, while recombinant alpha 2-interferon (reaferon) showed no LMIF activity.