The emerging role of follicular CD4 T cells in the immune system: a comprehensive analysis in different diseases and anatomic compartment in the era of Covid19

T follicular helper cells (TFH) are specialized subset of CD4 + T cells essential for the proper generation of germinal center (GC) reaction which eventually lead to the development of antigen specific memory B cell upon antigen stimulation. The present dissertation will perform a comprehensive analysis of the emerging role of TFH in the immune system analyzing their role in different diseases and anatomic compartment with a focus on SARS-CoV2. Only few studies in humans were able to provide a discrete description of the complex network of cytokines, chemokines and lymphocytes acting in tissues after antigenic challenge since most data derive from animal models. A better understanding of the biology of human immune system within tissues, where the actual immune responses take place, is mandatory to fill the gap of knowledge between animal and human models and to gain more insight into the basic immunology. I report published results of TFH analysis performed across the PhD course, starting with the analysis of mucosal immune dynamics in tonsils investigating the spatial positioning, frequency, and phenotype of immune cells after vaccination. Next, the increasing evidence of the active role of TFH also in the context of immunodeficiencies led us to further investigate their role in such condition. In this context I report a detailed immunophenotyped 6 analysis of children affected by Chromosome 22q11.2 deletion syndrome. Finally the emergence of SARS-Cov2 pandemic pushed the scientific community and ourselves in concentrating the efforts to dissecting the pathogenesis of this disease. I report the results of an important study about the immunology of Multisystem Inflammatory Syndrome in Children with COVID-19