IDENTIFICATION OF MONONUCLEAR-CELLS IN HUMAN-BLOOD .2. EVALUATION OF MORPHOLOGICAL AND IMMUNOLOGICAL ASPECTS OF NATIVE AND FORMALDEHYDE-FIXED CELL-POPULATIONS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 41  (3) , 567-574
Abstract
The presence of surface-associated Ig and Fc receptors on mononuclear cells from normal human blood was investigated by the direct immunofluorescence technique combined with phase-contrast microscopy. Formaldehyde-fixed cells were compared to unfixed cells and to cells preincubated at 37.degree. C. In the unfixed samples a separate population which showed Fc receptors in an immunofluorescence technique using a labeled antigen-antibody complex was detected. This cell population showed an atypical, i.e., not clearly membrane-associated, pattern of fluorescence with anti-Fab conjugates. This interaction most probably is due to autologous IgG molecules taken up by these cells from the donor serum. Using phase-contrast microscopy, these cells were morphologically distinct from lymphocytes and mature monocytes; they will be referred to as undefined mononuclear cells (UMC). After formaldehyde fixation or preincubation at 37.degree. C, the interaction of the UMC with anti-Fab conjugates could not longer be demonstrated. Mature monocytes show the same atypical fluorescence pattern with anti-Fab conjugates, but in contrast to the UMC the interaction persists after formaldehyde fixation or preincubation at 37.degree. C. No evidence was found for passive uptake of labeled IgG from conjugates by any mononuclear cell. F(ab'')2 fragments of IgG from antisera gave results similar to those obtained with intact IgG fractions. The morphology of the different cell subpopulations is described and their relative numbers in normal blood are given. Formaldehyde fixation proved to be a simple and useful procedure, especially for the determination of the number of B lymphocytes, because the Fc receptor of the undefined mononuclear cells does not give rise to confusion.