Whenever some phenomenon can be represented as a graph or a network it seems pertinent to explore how much the mathematical properties of that network impact the phenomenon. In this study we explore the same philosophy in the context of immunology. Our objective was to assess the correlation of “size” (number of edges and minimum vertex cover) of the JAK/STAT network with treatment effect in rheumatoid arthritis MESHD rheumatoid arthritis HP (RA), phenotype of viral infection MESHD and effect of immunosuppressive agents on a system infected with the coronavirus. We extracted the JAK/STAT pathway from Kyoto Encyclopedia of Genes and Genomes (KEGG, hsa04630). The effects of the following drugs, and their combinations, commonly used in RA were tested: methotrexate, prednisolone, rituximab, tocilizumab, tofacitinib and baricitinib. Following viral systems were also tested for their ability to evade the JAK/STAT pathway: Measles MESHD, Influenza A, West Nile virus, Japanese B virus, Yellow Fever MESHD Fever HP virus, respiratory syncytial virus, Kaposi’s sarcoma MESHD sarcoma HP virus, Hepatitis B MESHD Hepatitis HP and C virus, cytomegalovirus, Hendra and Nipah virus and Coronavirus. Good correlation of edges and minimum vertex cover with clinical efficacy were observed (for edge, rho= -0.815, R2= 0.676, p=0.007, for vertex cover rho= -0.793, R2= 0.635, p=0.011). In the viral systems both edges and vertex cover were associated with acuteness of viral infections MESHD. In the JAK/STAT system already infected with coronavirus, maximum reduction in size was achieved with baricitinib. To conclude, algebraic and combinatorial invariant of a network may explain its biological behaviour. At least theoretically, baricitinib may be an attractive target for treatment of coronavirus infection MESHD.