Comparison of lymphocyte isolation methods for endoscopic biopsy specimens from the colonic mucosa.

An ideal method of immune cell isolation should provide maximum cell yield without disturbing functional properties. Intestinal endoscopic biopsies, in contrast to surgical samples, allow the study of all disease stages but have the drawback of a minimum amount of tissue available, making protocol optimization mandatory. We compared for the first time two methods of separation of colonic epithelium and five methods of lamina propria cell isolation for colonic biopsy specimens (mechanical, enzymatic and organ culture protocols). Lymphocyte number, viability and phenotype (CD45+, CD103+, CD3+, CD4+, CD8+, CD19+, CD16-56+) were analyzed by flow cytometry. Neither of the two epithelial detachment protocols achieved proper epithelial separation, though the high intensity ion chelation method was more accurate. Maximum cell yield of lamina propria lymphocytes without phenotypic modification was obtained with overnight smooth enzymatic digestion. High dose collagenase incubation caused a marked decrease in CD4+ lymphocytes of the lamina propria as compared to low enzymatic method (p=0.004). Mechanical and biopsy culture are not advisable methods because of the low cell yield, and phenotypic alterations and high contamination rate, respectively.