Abstract
Since the TH1 and TH2 immune response paradigm, more host immunological pathways have been discovered including TH17, TH9, TH22, Tr1, Treg, Tfh, TH3, and TH1like recently. These immunological pathways’ functional clinical importance is not clearly known. In this article, the host immunological pathways are reorganized to get a clear picture. There are four eradicable immune responses: TH1/TH2/TH22/THαβ which correspond to four tolerable immune responses: TH1Like/TH9/TH17/TH3. TH1/TH1like provides immunity against intracellular bacteria or protozoa and is related to type4 delayed-type hypersensitivity. TH1 immunity includes M1 macrophages, CTLs(Tc1), IFN-γ producing CD4 T cells, and IgG3 producing B cells. TH1Like immunity includes M2 macrophages, suppressive CTL, IFN-γ/TGF-β producing CD4 T cells, and IgA1 producing B cells. TH2/TH9 provides immunity against helminths and is related to type1 immediate allergy. TH2 immunity includes eosinophils(iEOS), basophils/mast cells(MCct), IL-4 producing CD4 T cells, and IgE/IgG4 producing B cells. TH9 immunity includes eosinophils (rEOS), basophils/mast cells(MCt), IL-9 producing CD4 T cells, and IgA2 producing B cells. TH22/TH17 is an immunity against extracellular bacteria or fungi and is related to type3 immune-complex hypersensitivity. TH22 immunity includes neutrophils(N1), IL-22 producing CD4 T cells, and IgG2 producing B cells. TH17 immunity include neutrophils(N2), IL-17 producing CD4 T cells, and IgA2 producing B cells. THαβ/TH3 is an immunity against viruses and is related to type2 antibody dependent cytotoxic hypersensitivity. THαβ immunity includes stimulatory NK cells(NKl), CTLs(Tc2), IL-10 producing CD4 T cells, and IgGl producing B cells. TH3 immunity includes regulatory NK cells(NK2), suppressive CTLs, IL-10/TGFβ producing CD4 T cells, and IgA1 producing B cells. THfh is the stimulatory pathway to initiate adaptive immunity. Cytokines can help to drive initiatory immunities to eradicable immune reactions. Another inhibitory pathway Treg is the key player which is used to change immune responses to tolerable immune responses which generate milder cytokines and other immune mediators to avoid severe destruction of tissue-organ during any chronic large scale infection. This 4×2+2, the whole diagram of host immunological pathways, describes initiatory, eradicable, regulatory, and tolerable immune responses.