Contact-dependent expression of actin in chicken lymphocytes in vitro

The presence of actin in chicken bursa, thymus and spleen cells has been confirmed using quantitative neutralization absorptions of anti-actin antibody (AAA) with frozen-thawed preparations of these three cell types. Spleen cells were more effective than thymus or bursa cells in reducing the AAA titre. Cell suspensions of these organs were allowed to settle onto a glass slide, air-dried and stained with AAA. Immunofluorescence was restricted to cell borders at points of contact with other cells. This staining was reversibly inhibited by cytochalasin B but not colchicine. The higher content of actin in spleen cells demonstrated by the absorption experiments was reflected in their more rapid expression of actin during smear formation, and the relative resistance of this to cytochalasin B treatment, compared to thymus and bursa preparations. These findings further support the proposition that actin expression is a function of lymphocyte maturation.