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Macrophage activities in sarcoma 180-bearing mice and EL4-bearing mice
Abstract:
Four types of macrophage activities were studied in sarcoma 180-bearing ICR mice and EL4-bearing C57BL mice. Sarcoma 180 cells grow very slowly and do not metastasize, while EL4 cells grow very rapidly and metastasize rapidly to the liver. Chemotactic activity of macrophages was significantly reduced from an early stage in both sarcoma 180-bearing ICR mice and EL4-bearing C57BL mice as compared with that in normal mice. Digestive activity, which was determined by following O2- production by chemiluminescence measurements was also reduced from an early stage in tumor-bearing mice, whereas no reduction of engulfment activity of microorganisms was observed until an advanced stage in both sarcoma 180-bearing mice and EL4-bearing mice. In contrast enhancement activity of macrophages in the blastogenic response of spleen lymphocytes to bacterial lipopolysaccharide was retained at the normal level at the early stage of the tumor graft and was reduced in later stages. These results suggest that activities of Ia-negative macrophages were at first depressed generally in tumor-bearing hosts and later the activities of Ia-positive macrophages were depressed by factor(s) which might be produced by tumor cells.
Insights
Macrophage immune functions like chemotaxis and digestion are impaired early in tumor-bearing mice. Later, macrophage enhancement activity declines, suggesting tumor-derived factors affect different macrophage types sequentially.
Area of Science:
- Immunology
- Cancer Biology
- Cellular Biology
Background:
- Macrophages play a crucial role in immune responses against tumors.
- Tumor progression can significantly alter macrophage function.
- Understanding these alterations is key to developing effective cancer immunotherapies.
Purpose of the Study:
- To investigate the impact of tumor growth on various macrophage activities.
- To differentiate the effects on different macrophage populations (Ia-negative and Ia-positive).
- To identify potential mechanisms by which tumors suppress macrophage functions.
Main Methods:
- Comparison of macrophage activities (chemotaxis, digestion, engulfment, and enhancement) in tumor-bearing mice (Sarcoma 180 and EL4) versus normal mice.
- Assessment of O2- production via chemiluminescence for digestive activity.
- Evaluation of blastogenic response of spleen lymphocytes to lipopolysaccharide for enhancement activity.
Main Results:
- Macrophage chemotactic and digestive activities were reduced early in both slow-growing (Sarcoma 180) and rapid-growing (EL4) tumor models.
- Engulfment activity remained largely unaffected until advanced tumor stages.
- Macrophage enhancement activity was preserved initially but declined in later stages of tumor growth.
Conclusions:
- Tumor-bearing hosts exhibit a general depression of Ia-negative macrophage activities early on.
- Later stages show depression of Ia-positive macrophage activities, potentially mediated by tumor-secreted factors.
- These findings highlight a sequential impairment of macrophage functions during tumor development.