The monoclonal antibody-producing cell type is a hybridoma cell. Details:

• Hybridoma cells are created by fusing an antibody-producing B lymphocyte (from an immunized animal, typically a mouse) with an immortal myeloma (cancerous) cell. This fusion yields a single cell line that can both secrete a single type of antibody and proliferate indefinitely.

• The resulting hybridoma thus acts as a perpetual factory for a monoclonal antibody with defined specificity, enabling large-scale production in culture or in vivo (hybridomas can be grown in culture or introduced into animals for ascites production, though modern methods emphasize in vitro culture).

If you’d like, I can summarize how this process compares to recombinant antibody production using different mammalian cell lines (e.g., CHO cells) and the contexts in which each approach is used.