An immunohistochemical study of chick primordial germ cells using the mouse antiserum against chick embryonic gonads.

We established a mouse antiserum by immunizing BALB/c mice with sexually undifferentiated 6-day chick embryonic gonads. The antiserum had a higher affinity to the plasma membrane and cytoplasm of primordial germ cells (PGCs) than to the somatic cells in 6-day chick gonads. PGCs at this stage appear to have a higher specificity with more antigenic capacity than gonadal somatic cells; thus, the antiserum should be useful as a cell marker of chick PGCs. Subsequently, an immunohistochemical examination of PGCs settling in the genital ridges of chick embryos was carried out by the use of the antiserum. The reaction was clearly detected in the plasma membrane and cytoplasm of 5-day PGCs. After sexual differentiation, the reaction changed in distribution in females. At 8 days, it was limited to the perinuclear region of PGCs. In males, although the reaction persisted for longer period than in females, only a weak reaction was detectable at 9 days. These results suggest that the occurrence of periodic molecular changes may be different between male and female PGCs.