Immune cell quantitation in normal breast tissue lobules with and without lobulitis

Area of Science:

• Immunology
• Breast Biology
• Tissue Microenvironment

Background:

• The immune microenvironment is studied in breast cancer, but its role in normal breast tissue is poorly understood.
• Cellular immune components and their localization in non-malignant breast tissue require further investigation.

Purpose of the Study:

• To quantify and localize cellular immune components within normal breast lobules.
• To compare immune cell densities in lobules with and without visible immune infiltrates (lobulitis).

Main Methods:

• Analysis of 11 normal breast tissue samples, assessing up to ten lobules per sample.
• Quantification of B cells (CD20), cytotoxic T cells (CD8), helper T cells (CD4), dendritic cells (CD11c), leukocytes (CD45), and monocytes/macrophages (CD68) using digital image analysis.
• Comparison of immune cell densities between lobules with and without lobulitis.

Main Results:

• Immune cells were predominantly localized to lobules, not stroma, in all normal samples.
• Most lobules contained CD8+, CD11c+, CD45+, and CD68+ cells, with fewer CD4+ and CD20+ cells.
• Lobules with lobulitis exhibited significantly higher densities of CD4+, CD8+, CD20+, and CD45+ cells, but not monocytes/macrophages or dendritic cells.
• Cytotoxic T cells (CD8+) and dendritic cells (CD11c+) were closely associated with the lobule epithelium.

Conclusions:

• Normal breast tissue harbors a dynamic mucosal immune system with myeloid and lymphoid cells localized to lobules.
• Lobulitis in normal breast tissue is associated with an increase in adaptive immune cells (B and T cells).
• These findings highlight the immune activity present even in non-malignant breast tissue.