The challenge encountered lies in cellular aggregation and clumping subsequent to incubation with Cytofix/Cytoperm BD Biosciences. Despite attempts to mitigate the issue through pipetting, the cells adhere stubbornly to the pipette tips, rendering this approach ineffective. Additionally, vortexing fails to disperse the clumps as they adhere to the tube surfaces. Notably, this clumping phenomenon is not observed prior to the addition of the BD reagent.