Human IgG1 Lambda Isotype Control Antibody [AP]

Background: The ability to acquire fully human monoclonal antibodies ( mAbs) with pre-defined specificities is critical to the development of molecular tags for the analysis of receptor function in addition to promising immunotherapeutics. Yet most of the arriving affinity maturated and complete human immunoglobulin G (IgG) molecules, which are actually derived from single human B cells, have not widely been used to study the conserved self antigens (Ags) such as CD152 ( cytotoxic T lymphocyte antigen-4, CTLA-4) because proper hosts are lacking. Results: Here we developed an optimized protocol for site-directed in vitro immunizing peripheral blood mononuclear cells (PBMC) by using a selected epitope of human CD152, an essential receptor involved in down-regulation of T cell activation. The resultant stable trioma cell lines constantly produce anti-CD152 mAb (gamma 4 lambda huCD152), which contains variable (V) regions of the heavy chain and the light chain derived from the VH3 and V lambda human germline genes, respectively, and yet displays an unusual IgG4 isotype. Interestingly,gamma 4 lambda huCD152 has a basic pI not commonly found in myeloid monoclonal IgG4 lambda s as revealed by the isoelectric focusing ( IEF) analysis. Furthermore,gamma 4 lambda huCD152 binds specifically, with nanomolar affinity, to an extracellular constituency encompassing the putative second complementarity determining region (CDR2) of CD152, whereby it can react to activated CD3(+) cells. Conclusion: In a context of specific cell depletion and conditioned medium, in vitro induction of human Abs against a conserved self Ag was successfully acquired and a relatively basic mAb,gamma 4 lambda huCD152, with high affinity to CDR2 of CD152 was thus obtained. Application of such a human IgG4 lambda mAb with designated CDR2 specificity may impact upon and prefer for CD152 labeling both in situ and ex situ, as it does not affect the binding of endogenous B7 ligands and can localize into the confined immunological synapse which may otherwise prevent the access of whole IgG1 molecules.

Polymorphic diversity in antibody constant domains has long been defined by allotypic motifs that cross react with the sera of other individuals. Improvements in sequencing technologies have led to the discovery of a large number of new allelic sequences that underlie this diversity. Many of the point mutations lie outside traditional allotypic motifs suggesting they do not elicit immunogenic responses. As antibodies play an important role in immune defense and biotechnology, understanding how this newly resolved diversity influences the function of antibodies is important. This review investigates the current known diversity of antibody alleles at a protein level for each antibody isotype as well as the kappa and lambda light chains. We focus on evidence emerging for how these mutations perturb antibody interactions with antigens and Fc receptors that are critical for function, as well as the influence this might have on the use of antibodies as therapeutics and reagents.