CTLA4 and B-cell chronic lymphocytic leukemia: The search strategy will consist of the following keywords and their respective synonyms; chronic lymphocytic leukemia, anti-PD-1 drugs (nivolumab, Pembrolizumab, Pidilizumab, Atezolizumab, Avelumab), anti-PD-L1 drugs (Atezolizumab, Avelumab, Durvalumab), anti-CTLA-4 drugs (Ipilimumab, Tremelimumab) anti-LAG-3 and anti-TIM-3 drugs and adverse events.