**Preface to "Immunophenotyping in Autoimmune Diseases and Cancer"**

The mammalian immune system is a Janus-faced network of well-coordinated, highly specialized cells and biomolecules. The sensitive balance of reactive and suppressive signals maintains homeostasis in the physiological state. Under pathological conditions, however, responsiveness can escalate in autoimmune diseases or remain suppressed in cancer. In severe autoimmunity, the overwhelming immune response leads to devastating diseases such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, and sclerosis multiplex. Conversely, immune cells, e.g., professional antigen-presenting cells and cytotoxic T cells, are not able to execute their physiological function in cancer. Recent progress in fluorescence flow cytometry and mass cytometry has contributed to a high-dimensional resolution of the complex immunophenotype both in autoimmune diseases and in cancer. We called authors to publish their latest achievements associated with the perturbance of the regulation of immune activation and the discovery of rare subpopulations of both innate and adaptive immune players in autoimmune diseases and cancer. The online version of the Special Issue can be found at https://www.mdpi.com/journal/ijms/special issues/Immunophenotyping.

> **G´abor J. Szebeni, L´aszl ´o G. Pusk´as** *Editors*

*Review*
