An immunohistochemical study of HLA-DR and α₁-antichymotrypsin- positive cells in the pulp of human non-carious and carious teeth

The condition of the pulp tissue was classified into seven groups according to the progression of carious lesions from stages S0 (non-carious teeth) to S6 (exposed pulp). There was a small number of anti-HLA-DR antibody-positive cells in the pulp of the early carious teeth, and a markedly increased number at S5 and S6. The recruitment of a large number of anti-HLA-DR cells concomitant with a marked increase of other kinds of immunocompetent cells in the pulp of late-stage caries might indicate the occurrence of antigen presentation followed by both cell-mediated and humoral immune reactions. The number of anti-α₁-antichymotrypsin (ACT) antibody- positive macrophages showed a proportional increase with the development of caries, and these cells may be involved in protecting against the tissue damage caused by proteases released from inflammatory cells, as well as having a defensive role by phagocytosis of toxic micro-organisms and damaged tissue residues. Thus anti-HLA-DR and anti-ACT antibody-positive cells might participate in both an efficient immune system and a tissue-protective mechanism in the human dental pulp.