Flow Cytometry Phenotypization of Intrathyroidal Lymphoid Infiltrate and Thyroidal Functional Status in Hashimoto Thyroiditis on Fine-Needle Cytology Samples

Objective: Intrathyroidal lymphoid infiltrate (TLI) may show qualitative and quantitative differences in Hashimoto thyroiditis (HT); thyroidal functional status (TFS) may differ among HT patients. The aim of this study has been to evaluate TLI in different TFS of HT.Methods: Flow-cytometry (FC) was applied to thyroidal fine-needle cytology samples (FNC) in 23 patients. TLI was analyzed using the following fluoresceinated antibodies: CD3, CD4, CD5, CD8, CD10, CD19, CD25, CD69, CD95 (FAS). TFS was determined by serum TSH, FT3, FT4 immunoassays, in specific clinical settings, to classify the patients as euthyroid (16) and hypothyroid (7). Pearson's correlation coefficient was used to evaluate possible correlations between CD4/CD8 ratio, CD4+ CD25+ CD69-: regulatory T (Treg) cells proportion, CD95 expression and TFS.Results: B-lymphocytes (CD19+, CD10±, CD5-, CD3-) were present in 18 cases, T-lymphocytes (CD19-, CD10-, CD5+, CD3+) in all the cases. CD4/CD8≥2:1 ratio was observed in 16 euthyroid and 3 hypothyroid; CD4/CD8≤1:1 ratio in none of euthyroid and in 4 hypothyroid. CD4+ CD25+ CD69- Treg cells proportion was lower in hypothyroid than in the euthyroid patients; CD4+, CD25+, CD95(FAS)+ were mainly expressed in hypothyroidism. Statistical analysis did not demonstrate associations among CD4/CD8 ratios, Treg cells proportions and CD95 expression in the two TFS. Conclusions: FNC may be used to assess TLI in HT. Intrathyroidal CD4/CD8 ≤ 1:1 ratio, CD4+, CD25+, CD69- cells reduction and CD95(FAS)+ are expression of Treg cells apoptosis and might be related to intense thyroidal damage and risk of hypothyroidism. Further studies are needed to assess their possible prognostic significance.