A Paired Flow Cytometry-Pathology Assessment for Immune Cell Detection in Intestinal Biopsies: Proof of Principle

Accurate quantification of immune cell subpopulations is essential for understanding immune responses in research and clinical settings. Flow cytometry (FC) is widely used for immune cell phenotyping, providing rapid and quantitative single-cell resolution. However, tissue-based pathological assessment offers additional spatial and morphological context that is often necessary for a comprehensive understanding of immune cell distribution. Traditionally, these methods are applied separately to different specimens, limiting direct comparative analysis. Here, we describe a simple combined approach to immune cell quantification that integrates both FC and pathology analysis within the same tissue specimen of colon biopsies. Tissue samples were divided into two portions: one processed into a single-cell suspension for FC-based characterization of CD45⁺, CD3⁺, CD4⁺, and CD8⁺ T cells and another formalin-fixed, paraffin-embedded (FFPE), and analyzed with hematoxylin and eosin (H&E) for eosinophils and immunohistochemistry (IHC) for CD4 and CD8. A pilot analysis of 10 samples shows high concordance of the results taken from the two methods, allowing for cross-validation between methodologies and improved diagnostic accuracy. This proof-of-principle study demonstrates the feasibility of an integrated workflow that combines FC and pathology for immune cell quantification, which provides assessment of immune cell populations from the limited material of intestinal biopsies with potential for improved diagnostic accuracy.