Aim To analyse phenotypic characteristics of antigen-presenting cells (APC), isolated from human periapical lesions by flow cytometry and immunocytochemistry.
Methodology Sixteen periapical lesions were digested for 15 min with 0.05% collagenase. Mononuclear cells, separated from other inflammatory cells by density centrifugation, were processed for flow cytometry and/or immunocytochemistry. Single and double immunostainings were performed using monoclonal antibodies specific for human CD45, CD3, CD19, CD14, HLA-DR, CD1a, CD83 and CD123.
Results Antigen-presenting cells (HLA-DR+ cells) represented 32.9 ± 17.8% of total mononuclear cells. Amongst them, B cells (HLA-DR+ CD19+) were the predominant APC population, followed by activated macrophages (HLA-DR+ CD14+), dendritic cells (DC) (HLA-DR+ CD14− CD19− CD3−) and activated T cells (HLA-DR+ CD3+). Based on the predominance of T cells (CD3+) or B cells and plasma cells (CD19+ and CD19lo, respectively) amongst mononuclear cell infiltrates, lesions were divided into T- and B-types. The percentage of DC in T-type lesions (27.1 ± 6.8% of total HLA-DR+ cells) was higher, compared with B-type lesions (10.3 ± 5.2%) (P < 0.01). Within the DC population, the percentages of CD1a (Langerhans cell type) and CD123 (probably plasmacytoid DC type) did not differ significantly between the groups (P > 0.05). However, the percentage of mature DC (CD83+) was significantly higher in T-type periapical lesions (P < 0.05).
Conclusion Flow cytometry and immunocytochemistry are suitable methods for phenotypic analysis of APC after their isolation from human periapical lesions. APC, that were phenotypically heterogeneous, constituted a significant component of infiltrating cells. Lesions with the predominance of T cells were characterized by a higher proportion of mature DC (HLA-DR+CD83+ cells) than lesions with predominance of B cells/plasma cells.