Harnessing the immune system's arsenal: producing human monoclonal antibodies for therapeutics and investigating immune responses

Sullivan, Meghan; Kaur, Kaval; Pauli, Noel; Wilson, Patrick C.

Whereas hybridoma technology evolved to eventually produce human antibodies, another technology went straight to the source (human B cells), even in its earliest forms. In 1977, Steinitz and colleagues developed approaches to virally transform human B cells, making immortal cell cultures of human B cells [14] . At the time, Rosén and colleagues had recently shown that Epstein-Barr virus (EBV) transformation of human B cells led to antibody secretion [15] . Steinitz et al. took this observation to the next level, making cultures that produced polyclonal mixtures of human antibodies that were reactive to an antigen of interest. Serial dilution down to one single cell clone from the starting pool of B cells enabled researchers to apply this technology to monoclonal antibody production. When combined with flow cytometry using fluorescently labeled "bait" to sort enriched reactive cells prior to EBV immortalization, the frequency of specific B cell lines generated was substantially improved [16] . Much later, Traggiai, Lanzavecchia and colleagues enhanced the efficiency of EBV transformation by providing innate immune stimulation using CpG (a Toll-like receptor 9 agonist) in combination with EBV treatment [17] . This and similar methods allow for the relatively large-scale transformation of human memory B cells into monoclonal antibody-secreting cell lines. Importantly, this technology allows researchers to quickly identify potential sources of clinically relevant antibodies. For instance, following the severe acute respiratory syndrome (SARS) epidemic, this same group screened patients for serum reactivity to the virus and then used the enhanced-EBV technology to immortalize specific memory B cells [17] . More recently, an EBV-independent method of B cell immortalization was described. In this method, investigators manipulated cellular pathways that control B cell survival using transgenes and successfully generated transformed B cell lines [18] .