Requirements for the generation of memory B cells in vivo and their subsequent activation in vitro for the production of antigen-specific hybridomas

Hybridoma technology for the generation of rodent mAbs via classical fusion

Monoclonal antibodies (mAbs) have proven to be instrumental in the advancement of research, diagnostic, industrial vaccine, and therapeutic applications. The use of mAbs in laboratory protocols has been growing in an exponential fashion for the last four decades. Described herein are methods for the development of highly specific mAbs through traditional hybridoma fusion. For ultimate success, a series of simultaneously initiated protocols are to be undertaken with careful attention to cell health of both the myeloma fusion partner and immune splenocytes. Coordination and attention to detail will enable a researcher with basic tissue culture skills to generate mAbs from immunized rodents to a variety of antigens (including proteins, carbohydrates, DNA, and haptens) (see Note 1). Furthermore, in vivo and in vitro methods used for antigen sensitization of splenocytes prior to somatic fusion are described herein.

Generation of monoclonal antibodies to human lymphocyte cell surface antigens using insect cells expressing recombinant proteins

We have expressed human CD40 and human B7 in insect cells using the baculovirus expression system and have used these insect cells to immunize mice for the generation of monoclonal antibodies. We demonstrate here that specific monoclonal antibodies to human CD40 and human B7 were obtained using this approach. One significant advantage of this method is that immunizing mice with insect cells did not evoke an immune response to human cells and, therefore, EBV-transformed human B cells could be used to screen for specific antibody production by the hybridoma clones.

A high-affinity human monoclonal IgM antibody reacting with multiple strains of Mycoplasma hominis

Human monoclonal antibodies were produced against Mycoplasma hominis by in vitro immunization of peripheral blood lymphocytes from a healthy seropositive donor using low amounts of antigen (5 ng/ml). The immune B lymphocytes were subsequently immortalized by Epstein-Barr virus transformation followed by somatic cell fusion. Using this procedure, several specific anti-M. hominis monoclonal antibodies of mu isotype were obtained exhibiting apparent affinity constants as high as 3 x 10(9)M-1. The productivity of a number of different hybridomas was determined to be in the range 7-22 micrograms x (24 hr x 10(6) cells)-1. The specificity of one antibody, 129.1, was further characterized by enzyme-linked immunosorbent assay against several different species of Mycoplasma and by Western blot analysis. The antibody specifically bound to a protein of Mr 100,000 present in 10 of 12 different strains of M. hominis.

High yields of specific hybridomas obtained by electrofusion of murine lymphocytes immunized in vivo or in vitro

We have studied the use of electrofusion to obtain hybridomas producing antigen-specific antibodies after immunization of murine lymphocytes in vitro. Under optimal conditions fusion frequencies of the order of magnitude of 10(-3) were obtained, which is approximately 80-fold higher than the mean value obtained with fusion induced by polyethylene glycol. The number of antigen-specific hybridomas was also increased in a comparable way. The high yields of specific hybridomas observed with electrofusion were independent of the immunization procedure, the antigen or the hapten of interest, or the sources of the lymphocytes. The data presented in this paper indicate that electrofusion may be an extremely attractive alternative method for immortalization of human lymphocytes following immunization in vitro.

Optimal conditions for the generation of monoclonal antibodies using primary immunisation of mouse splenocytes in vitro under serum-free conditions

We have further optimised the serum-free in vitro immunisation system described by Ossendorp et al. (J. Immunol. Methods 91, 257, 1986) for the generation of hybridomas secreting specific antibodies. Thyroglobulin and the hapten 2-phenyl-5-oxazolone coupled to chicken serum albumin were used as antigens. For an optimal outgrowth of antigen-specific B cells the presence of T cells, thymocyte-conditioned medium and antigen are required. The addition of supernatant from EL-4 cells (stimulated by phorbolmyristate acetate) inhibits the outgrowth of antigen-specific B cells. Using six-well plates with a surface area of 10 cm2 per well, an optimal IgM response was obtained when 10(7) splenocytes in a total volume of 2 ml/well were cultured for 3 days in the presence of antigen and thymocyte-conditioned medium. Increasing the concentration of cells whilst maintaining a constant surface area resulted in a decreased response.