OBJECTIVETo observe the effects of iodine/selenium on the function of antigen presentation of peritoneal macrophages in rats and explore the immunological mechanisms of iodine/ selenium's role in pathogenesis of autoimmune thyroid diseases (AITD).

METHODSFemale Lewis rats were randomly divided into four groups including (1) low selenium and normal iodine group (L(sE)N(I)) (2) low selenium and high iodine group (L(Se)H(I)) (3) normal selenium and normal iodine group (N(Se)N(I) ) (4) normal selenium and high iodine group (N(Se)H(I)). All rats were fed by a special diet with lower selenium and iodine in it and drunk ion-free water containing different levels of iodine and selenium for 3 months. Peritoneal macrophages of each group and OVA allergized T cells were prepared and cultured together. Then the function of antigen presentation were estimated by detecting the levels of IL-2 in the culture supernatant. The levels of the expression of co-stimulator CD86 in the spleen of each group were determined by RT-PCR.

RESULTSThe level of IL-2 in the supernatant in N(Se)H(I) (43.22 +/- 3.27) pg/ml was much stronger than N(Se)N(I) [the level of IL-2 was (25.74 +/- 2.45) pg/ml, P < 0.05]. The level of IL-2 in L(Se)N(I) (15.79 +/- 2.13) pg/ml was significantly lower than N(Se)N(I) (P < 0.05). The expression of CD86 mRNA in N(Se)H(I) (CD86/beta-actin: 0.52 +/- 0.10) were higher than N(Se)N(I) (CD86/beta-actin: 0.35 +/- 0.04), P < 0.05.

CONCLUSIONSHigh iodine could promote the presentation function of macrophages to a higher state than normal. Therefore, high iodine intake might become an importantly inducing factor in thyroid autoimmunity. Low selenium could weaken the ability of recognizing and presenting OVA antigen of peritoneal macrophages which might destroy immunological homeostasis and thus the low selenium intake might also become an inducer of AITD.