CTLA4 and Autoimmunity: By examining the clusters which contain these articles, we assessed whether clusters represent the contents of these articles: article A [24] on the discovery of PD-1, article B [23] on the function of CTLA-4, article C [22] that showed antitumor activity of anti-CTLA-4 antibody in mice, article D [21] on the involvement of PD-1 in autoimmunity; article E [20] on PD-1 and immunosuppression, and article F [19] on the antitumor effect of PD-L1 inhibitors in mice.