RhoH does not affect thymocyte development through regulation of αLβ2 integrin-mediated adhesion. (A) Relative adhesion of thymocytes to the immobilized αLβ2 ligand ICAM-1 and to the α4β1 ligand VCAM-1. Integrins were activated by treatment with 2 mM Mn²⁺ or 100 ng/mL PMA as indicated. Adhesion of wild-type (RhoH ⁺/⁺), heterozygous (RhoH^+/−), and homozygous RhoH-null thymocytes (RhoH ^−/−) was indistinguishable at all conditions tested. Error bars show the standard deviation (n [RhoH^+/+]/[RhoH^+/−]/[RhoH^−/−]: 1/2/3. (B) Relative adhesion of T-cell blasts to the endothelial cell line bEnd5 and the ICAM-1–deficient endothelial cell line bEndI1.1 (ICAM1^−/−). Adhesion was stimulated by treating the endothelial cells with TNF. Antibodies against α4-integrin and LFA-1 were used to determine the specific contribution of these adhesion receptors to the attachment. An unrelated antibody was added as a control for nonspecific effects. Wild-type (RhoH⁺/⁺), heterozygous (RhoH^+/−), and homozygous (RhoH^−/− ) RhoH-null T cells showed indistinguishable adhesion at all conditions tested. Error bars show the standard deviation (n [RhoH^+/+]/[RhoH^+/−]/[RhoH^−/−]: 2/2/4. (C)Thymocytes of 6- to 10-week-old β2-integrin-null, RhoH-null, and β2-integrin-RhoH double-knockout mice were analyzed for the expression of CD4 and CD8 by FACS. Bar graph presents the absolute cell numbers of each population. Error bars indicate the standard deviation (n [β2^−/−]/[RhoH^−/−]/[β2^−/−RhoH^−/−]: 3/3/3. (D) Expression of CD5 and amount of CD5^low thymocytes in 6- to 10-week-old β2-integrin-null, RhoH-null, and β2-integrin-RhoH double-knockout mice. Error bars indicate the standard deviation (n [β2^−/−]/[RhoH^−/−]/[β2^−/−RhoH^−/−]: 3/3/3.