Change in tumour cell-lymphocyte interactions with age

Area of Science:

• Immunology
• Cancer Biology
• Aging Research

Background:

• Leukophagocytosis, the engulfment of leukocytes by other cells, is a poorly understood phenomenon.
• Tumor cells can exhibit phagocytic activity, potentially influencing immune responses.
• Age-related changes in immune cell function are well-documented but the interaction with tumor phagocytosis requires further investigation.

Purpose of the Study:

• To investigate the relationship between animal age and the leukophagocytic activity of tumor cells.
• To determine if aging affects the susceptibility of leukocytes to phagocytosis by tumor cells.
• To explore the potential impact of age-related leukophagocytosis on overall immune function.

Main Methods:

• Splenic leukocytes from C3H mice of varying ages were isolated and depleted of macrophages.
• Two tumor cell lines, P388D1 (mouse macrophage lymphoma) and LAZ-559 (human B cell lymphoma), were used as effector cells.
• Tumor cells were co-cultured with leukocytes for 4 hours, and the percentage of phagocytic tumor cells was quantified using cytospin preparations.

Main Results:

• Phagocytic activity of P388D1 cells increased significantly with leukocyte age, from 10% in 1-week-old mice to 28% in 35-week-old mice.
• LAZ-559 cells also demonstrated increased phagocytosis of older leukocytes, rising from 5% to 17% across the same age range.
• Leukocyte susceptibility to phagocytosis was detectable within 30 minutes and increased with incubation time, leading to a 38% and 29% reduction in leukocyte numbers by P388D1 and LAZ-559, respectively, after 4 hours.

Conclusions:

• An age-related decline in immune function is associated with enhanced leukophagocytosis by tumor cells.
• The increased engulfment of leukocytes by tumor cells in older animals may contribute to immune system impairment.
• This phenomenon highlights a potential mechanism by which aging compromises immune surveillance and response.