We determined the effects of temperature shifts on the kinetics of the numbers of antibody-secreting cell (ASC) in the olive flounder Paralichthys olivaceus immunised with formalin-killed Edwardsiella tarda. When fish that were acclimated to $22^{circ}C$ and immunised at that temperature were transferred to a lower temperature ($12^{circ}C$) at a various times (immediately, 1, 2 or 4 weeks) after immunisation, both further differentiation of B cells and secretion of antibody from the ASC developed at $22^{circ}C$ were suppressed at $12^{circ}C$. However, in the converse experiment ($12^{circ}C$ to $22^{circ}C$), the magnitude of the humoral immune response was recovered independent of the time of the transfer after immunisation at low temperature, even though the peak levels of each transferred group did not reach the level found in $22^{circ}C$ control group. The results were confirmed by counting the number of specific antibody secreting cells (SASC) in the spleen. This study provides the evidences of the immune reaction that the potential for antibody production in B cells of flounder, the most important species in aquatic industry of Korea, immunized at high temperature is suppressed by subsequent exposure to low temperature and that low temperature-induced humoral immuno suppression can be reversed by exposure to a higher temperature.