During the development of COVID-19 caused by SARS-CoV-2 infection from mild disease to severe disease, it can trigger a series of complications and stimulate a strong cellular and humoral immune response. However, the precise identification of blood immune cell response dynamics and the relevance to disease progression in COVID-19 patients remains unclear. We propose for the first time to use changes in cell numbers to establish new subgroups, which were divided into four groups: first from high to low cell number (H_L_Group), first from low to high (L_H_Group), continuously high (H_Group), and continuously low (L_Group). It was found that in the course of disease development. In the T cell subgroup, the immune response is mainly concentrated in the H_L_Group cell type, and the complications are mainly in the L_H_Group cell type. In the NK cell subgroup, the moderate patients are mainly related to cellular immunity, and the severe patients are mainly caused by the disease, while severe patients are mainly related to complications caused by diseases. Our study provides a dynamic response of immune cells in human blood during SARS-CoV-2 infection and the first subgroup analysis using dynamic changes in cell numbers, providing a new reference for clinical treatment of COVID-19.

Cancer immunotherapy with immune checkpoint inhibitors has revolutionized traditional cancer therapy. Although many patients have achieved long‐term survival benefits from treatment with immune checkpoint inhibitors, there are still some patients who develop rapid tumor progression after immunotherapy, known as HPD. Here, we summarize the current knowledge on HPD after treatment with immune checkpoint inhibitors to promote a more thorough understanding of the disease. This review focuses on multiple aspects of HPD, especially the tumor microenvironment, with the hope that more reliable biomarkers and therapeutics will be established for HPD in the future.