Blood monocytes and tumor-infiltrating macrophages in human breast cancer: differences in activation level as assessed by lysozyme content.

The lysozyme content of tumor-infiltrating macrophages (TIM) from human breast carcinomas has been compared with that of blood monocytes both from breast cancer patients and tumor-free controls. Cells were identified as macrophages or monocytes with the use of rosetting reactions to detect receptors for the Fc portion of IgG and differentiation antigens, and lysozyme was detected by an immunoperoxidase technique on cytocentrifuge preparations of rosetted cells. Significantly more monocytes from patients with breast cancer contained lysozyme than monocytes from comparable controls, suggesting the presence of activated circulating blood monocytes. Conversely, TIM were virtually devoid of lysozyme. This lack of enzyme was not due to methodologic factors and may represent defective antitumor activity.