Persistent polyclonal B-cell lymphocytosis (PPBL) is an anomaly of the human immune system characterized by mildly elevated levels of white blood cells (called leukocytosis), chronic, stable absolute polyclonal B-cell lymphocytosis, elevated polyclonal IgM and binucleated cells. Persistent polyclonal B-cell lymphocytosis (PPBL) is an anomaly of the human immune system characterized by mildly elevated levels of white blood cells (called leukocytosis), chronic, stable absolute polyclonal B-cell lymphocytosis, elevated polyclonal IgM and binucleated cells.