CD44 IS NECESSARY FOR OPTIMAL CONTACT ALLERGIC RESPONSES BUT IS NOT REQUIRED FOR NORMAL LEUKOCYTE EXTRAVASATION

The in vivo administration of certain monoclonal antibodies (mAbs) aga inst the adhesion receptor, CD44, into normal mice induces both a modu lation of CD44 from the surface of peripheral lymphocytes, and a conco mitant increase in the amount of soluble CD44 in the serum. CD44-negat ive lymphocytes isolated from anti-CD44-treated mice exhibit normal ho ming patterns upon adoptive transfer, and are capable of reexpressing CD44 upon activation. The treatment of hapten-sensitized mice with ant i-CD44 mAb inhibits their ability to mount a cutaneous delayed-type hy persensitivity (DTH) response within the first 24 h after hapten chall enge. This inhibition reflects a block in both the edema and leukocyte infiltration of the cutaneous site of DTH, whereas the extravasation and accumulation of leukocytes in the draining lymph nodes progress no rmally. After 72 h, the leukocytes that extravasate into the site of a ntigen challenge express CD44. These results indicate that CD44 is not necessary for normal leukocyte circulation but is required for leukoc yte extravasation into an inflammatory site involving nonlymphoid tiss ue.