We adapted one of the in-vitro immunization methods to induce antibody responses and confirmed the success of the immunization by enzyme-linked immunosorbent assay (ELISA) without hybridization. We have previously reported several methods of in-vitro immunization using different conditioned media. Here we introduce another method of in-vitro immunization using a mixture of three types of supernatant (thymocytes, and adherent and non-adherent splenocytes of mouse). Splenocytes were immunized in-vitro by a recombinant human growth hormone (rhGH) with the above conditioned media, and the results by ELISA showed a much higher optical density than the other in-vitro immunization methods that we had previously reported. Humoral responses as a result of in-vitro immunization to soluble antigens were easily confirmed by ELISA using the above-conditioned media. This finding indicates that any other conditions thought to be critical by other researches may not be essential for in-vitro immunization.