RELATIVE DISTRIBUTION OF PLASMA-CELLS EXPRESSING IMMUNOGLOBULIN-G SUBCLASS MESSENGER-RNA IN HUMAN DENTAL PERIAPICAL LESIONS USING IN-SITU HYBRIDIZATION

Immunoglobulin G (IgG)-producing plasma cells are the predominant immu noglobulin secreting plasma cells in human dental periapical lesions, compared with immunoglobulin A-and immunoglobulin M-producing plasma c ells. In this study, the cells expressing mRNA, that encoded the disti nct IgG subclasses, were detected using an in situ hybridization techn ique in 25 periapical lesions. These lesions consisted of 14 periapica l granulomas and 11 radicular cysts. Four oligonucleotide probes were chemically synthesized from IgG subclass-specific hinge region genes t o ensure specificity of the probes. Plasma cells expressing mRNA, whic h coded for the IgG subclasses, were detected in formalin-fixed/paraff in wax-embedded sections. Background staining was negligible in all of the sections tested. The in situ hybridization method used in this st udy was both specific and sensitive for the detection of mRNA encoding each of the four distinct IgG subclasses, whereas the cells retained good morphology. The relative proportions of plasma cells expressing e ach of the IgG subclass-specific mRNAs in both granulomas and cysts we re as follows: IgG1 (57.4 and 55.5%); IgG2 (34.1 and 34.6%); IgG3 (4.0 and 4.3%); and lgG4 (4.0 and 5.5%). There were no significant differe nces between the percentages of plasma cells expressing each of the Ig G subclass mRNAs between the two types of lesions. IgG1 producing plas ma cells comprised the highest proportion of IgG-producing plasma cell s in both types of periapical lesion. IgG2-producing plasma cells were next in abundance, followed by plasma cells for either IgG3 or lgG4, which were in roughly equivalent numbers.