Abstract
The macrophage content of cell suspensions from naturally occurring mouse tumours has been assessed by the Fc-mediated phagocytosis assay, and the results compared with the individual tumour's capacity for spontaneous metastasis and with its pulmonary colonization potential after i.v. inoculation. It was found that these tumours differ in their properties from the transplantable fibrosarcomas studied previously by other investigators, in that the macrophage content of all the tumours was uniformly low, ranging from 2 to 9% (mean 4.2 +/- 1.8%) and there was no inverse correlation with frequency of spontaneous metastasis, which was low. When the tumours were inoculated i.v. there was also no correlation with colony-forming capability, which varied greatly between tumours. Lung secondary deposits contained 1.7-6% macrophages (mean 4.4 +/- 0.6%) with a lower phagocytic activity for antibody-coated red cells than in the primary tumour.
Highlights
It was found that these tumours differ in their properties from the transplantable fibrosarcomas studied previously by other investigators, in that the macrophage content of all the tumours was uniformly low, ranging from 2 to 9% and there was no inverse correlation with frequency of spontaneous metastasis, which was low
Fia. 2. (a) Light micrograph of macrophages following the ingestion of EA. x 250. (b) Tumour-cell culture consisting of islands of tumour cells with spaces between containing macrophages with ingested EA. x 100
Pi phagocytic indices of the primary tumour macrophages were all in the range 5-11 (Fig. 3). (The phagocytic index is the mean uptake of EA per cell, determined by examining 100 cells)
Summary
Latex-bead phagocytosis.-Tumour-cell cultures were exposed to latex beads (08,um diam.) in suspension The ingested beads were washed off, and phagocytic cells and the number of beads they contained were counted with a phase-contrast microscope. Sheep red blood cells (SRBC, Flow Labs) were washed in physiological normal saline and titrated with specific rabbit antiSRBC IgG to determine the maximum nonagglutinating concentration of antibody. This was 2-3 ,ug/ml but there was some variation between batches of SRBC. The red cells were diluted to 3% in saline and exposed for 30-60 min to IgG at the determined concentration at room temperature They were washed x 3 in saline by centrifugation. The number and size of deposits on the surface of the lungs were counted, and the colonization potential, in terms of size and number, graded on the following scale: Grading system for secondary (2°) deposits
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