Analysis of the human immune repertoire using human monoclonal antibodies

The investigations of the human immune response to cancer and other diseases have been hampered by the difficulty in determining the specificity of low-titered antibodies in serum, and the inability to define the specificity of individual lymphocytes. In order to study these issues, we developed the hybridoma technology so that human monoclonal antibodies (hMAb) could be reliably and reproducibly obtained. Using a variety of fusion partners of both mouse and human origin, a large number of human immunoglobulin-secreting hybrids have been generated. We have found that 5 to 10% of the hybridomas produced secrete hMAb reactive with antigens (Ag) expressed by human cells. Specificity analysis and cellular localization studies of the Ag have been performed for a large number of these hMAb, and several general points have emerged from our study: (A) A significant proportion of the evaluable B-cell repertoire is directed to the production of antibodies reactive with Ags expressed by human cells. (B) The great majority of these AGs have an intracellular location, and are broadly distributed, being expressed by both normal and malignant cells. (C) Intracellular and cell surface differentiation Ags and other Ags with restricted distribution have been defined by hMAb, including a series of cell surface and intracellular Ags not detected on normal cells. (D) The relationship of these findings to cancer is unclear as hMAb showing distinctive distributions have been generated from the lymphocytes of normal individuals as well as tumor-bearing patients. (E) hMAb with distributions distinct from any known mouse monoclonal antibodies (mMAb) have been obtained. These reagents may hold great promise for antibody-directed in vivo diagnosis and therapy of cancer and other diseases due to their unique specificity and decreased immunogenicity compared with mMAb.