CEBPZ and ocular melanoma: Furthermore, variability could also be linked to surface-exposure of CBF [32]: to test this hypothesis, we used the rabbit anti-rCBF serum (with high titre reactivity with OM and meningococcal cells and cross-reactivity with CBF proteins encoded by different alleles) to examine by FACS the surface-exposure of CBF in the different meningococcal strains.