C.M. Steel

Association between pregnancy-associated alpha2-glycoprotein (alpha2-PAG) and mixed leucocyte reaction determinants on the leucocyte surface.

α2-PAG is present on the surface of mononuclear blood leucocytes and can be demonstrated predominantly on B-lymphocytes and monocytes. Pretreatment of cells with antibody to α2-PAG leads to a marked reduction in Fc-rosette formation. Competitive blocking experiments with specific antisera reveal a particularly close asociation between α2-PAG and MLR (mixed leucocyte reaction) determinants on the cell surface. These findings suggest one mechanism whereby α2-PAG may modify cell-mediated immune responses.

Subsets of Human D Locus Products Identified by a Series of Monoclonal Antibodies

Abstract A series of monoclonal antibodies, prepared against the Burkitts lymphoma line Daudi, define antigens predominantly expressed on cells of the B lymphoid series. Four antibodies which react with HLA-DR or DR-like antigens have enabled the serological definition of at least two and possibly three distinct subsets of molecules. Of these four antibodies, one (DA6.164) defines a DR allotype associated epitope common to all DR types tested except DR 7 homozygotes. A second (DA6.147) recognizes a DR-like antigen which is expressed in abundance on B lymphoblastoid cells, weakly on peripheral blood B cells and not at all on activated T cells. Two further antibodies (DA6.231 and DA6.121), with indistinguishable specificity, detect an epitope apparently common to more than one set of DR molecules.

The use of detergents in velocity sedimentation of cell culture IgM

The biosynthetically radiolabelled secreted proteins of human lymphoblastoid cell lines have been analysed by sucrose gradient velocity sedimentation. The addition of detergent to the gradient buffer dramatically improves the recovery of immunoglobulins from cell line supernatants, allowing the gradient fractions to be analysed further both serologically and biochemically. The results of these analyses show that IgM is synthesised in the 19S form and can be clearly separated from other components which include free light chains. Immunoglobulin appears to form a much larger portion of the proteins secreted by human lymphoblastoid lines than has formerly been recognised, a finding which may be of practical importance for the development and exploitation of human monoclonal antibodies.

Methods of detecting mature human Ia-like antigen and their metabolic precursors

Ia antigens were shown to be present in the cell almost exclusively as mature alpha beta dimers which split into separate alpha and beta chains after boiling in SDS. In contrast metabolically labelling the cells with [35S]methionine resulted in only free alpha and beta chains being labelled. It is concluded that this widely used type of labelling, although useful for studying intermediate synthesis, should not be used for labelling mature cell surface molecules.

Monoclonal Anti-B Cell Antibodies: their Effects on Human Mixed Lymphocyte Reactions

Abstract Three monoclonal antibodies which recognise determinants on the surface of human B cells have been studied for their effect on mixed lymphocyte reactions (MLR). MLR inhibition was observed under a variety of conditions. While it was not possible to ascribe lymphocyte activation to a single determinant recognised by any of the antibodies, further analysis of the mechanisms involved in lymphocyte activation should be possible through the use of monoclonal reagents.