Monoclonal IgG Antibodies Influence the Migration Patterns of Lymphocytes in vivo

Abstract

Monoclonal antibodies (MoAb) are useful therapeutic agents for the treatment of a variety of human disorders, although the effector mechanisms responsible for the outcome of an efficient immunotherapy remain unclear. This study was designed to address the early effects of MoAb on the migration patterns of lymphocytes in vivo. The clearance profiles and tissue distribution of ¹¹¹In–labelled rat lymph node cells were examined in both normal and decomplemented allogeneic and semi–allogeneic recipients pre–injected with IgG2b (R3/13) or IgG2a (R2/15S) MoAb directed against the RT1A^a, the classical class I major histocompatibility complex antigen of the DA rat. Both MoAb were equally effective in not only augmenting the removal of DA and (DA × PVG)F₁ cells from the circulation and promoting their subsequent localization within the liver but also causing a significant degree of cell lysis during the early phase of cell clearance, even in decomplemented recipients. Although R3/13 and R2/15S are known to target erythrocytes differently in normal and cobra venom factor (CVF)–treated animals, no differences were observed in the migration behaviour of lymph node cells in allogeneic or semi–allogeneic hosts pre–injected with the same MoAb. Since rat lymphocytes express a much higher level of the RT1A^a antigen as compared with erythrocytes, we could not exclude a possible role of residual complement components in the circulation of CVF–treated rats that may have accounted for the observed antibody–dependent effects on target lymphocytes. On the basis of these findings we believe that the design and methodology employed in our present experimental opsonization system were inadequate to define clearly the mechanisms responsible for antibody–mediated removal and destruction of target lymphocytes in vivo.