Toll-like receptors (TLRs), as an important pattern recognition receptor (PRRs), are mainly expressed on the surface of macrophages and dendritic cells (DCs). Selective recognition of pathogen-related molecular patterns (PAMPs) constitutes the first barrier of immune system against pathogen invasion. TLR is a highly conserved type I transmembrane protein in many organisms, and 12 species have been found and cloned in mammals. Once the specific molecular structure of the pathogen is determined, TLR will activate a series of signal pathways downstream of it, and activate natural immune cells to produce inflammatory cytokines and interferon type I. TLR not only starts the natural immune response and controls the nature, intensity and duration of inflammatory response, but also promotes the maturation of DC by up-regulating MHCⅱⅱ class II molecules and * * * stimulators, and regulates the intensity and type of acquired immune response, thus becoming a bridge between the initial immune response and the acquired immune response. Over-activation or under-activation of TLR signal will lead to physical dysfunction and diseases. Many other signal paths participate in the strict regulation of TLR signals. Therefore, in-depth study of TLR signal transduction regulation has important theoretical significance and application value. As one of the second messengers in cells, Ca2+ regulates many important physiological processes. Calcium/calmodulin-dependent protein kinase Ⅱ (CAMKII) is a multifunctional silk/threonine protein kinase located downstream of calcium signal, which is widely distributed in most important organs and tissues. It is encoded by four independent genes α, β, γ and δ, with different splicing, resulting in as many as 24 different subtypes. CaMKII has many substrates, such as transcription factor CREB, ATF and other signal molecules p56Ick, SHP-2, STAT 1, etc. CaMKII can regulate many important physiological functions of the body, such as synaptic signaling, memory, substance metabolism, muscle contraction, gene expression and cell cycle regulation. Recent studies have shown that CaMKII plays an important regulatory role in the immune system, such as T cell activation and memory, DC maturation and antigen presentation. It has been proved that LPS(TLR4 ligand) stimulates calcium flow in the cytoplasm of mouse macrophages, which plays an important role in the production of TNF-α induced by LPS. Some studies also show that CaMKII can enhance the production of TNF-α induced by LPS in THP- 1 cells pre-stimulated by platelet activating factor (PAF). These studies indicate that Ca2+ and CaMKII may be involved in TLR4 signal. However, the role of calcium and CaMKII in the production of inflammatory cytokines and interferon type I induced by TLR ligands, and the interaction between Ca2+/CaMKII signaling pathway and TLR signaling pathway and its related mechanism are still unclear (question 1). MicroRNAs(miRNAs) are a large number of endogenous non-coding small rnas, which participate in many physiological and pathological processes. MiRNAs play an important role in the regulation of immune system function, including regulating the initial immune response of macrophages to foreign pathogens, the development, differentiation and function of lymphocytes. However, there are few reports about the regulation of DC maturation and function by miRNA. CaMKII has been proved to play an important role in the maturation and function of DC, but the research on miRNA and CaMKII has not been reported yet. We want to explore whether there are mirnas, which mirnas can play a regulatory role in the maturation and activation of DC, and stimulate the proliferation of T cells by directly acting on CaMKII (Question 2). Previous studies have shown that antigen stimulation can induce the increase of intracellular calcium current in DC, and both calcium and CaMKII can regulate the expression of MHC class II molecules in DC, indicating that there is a mutual regulation between Ca2+/CaMKII and MHC class II molecules. However, it is not clear whether MHCⅱⅱ molecules can induce the activation of CaMKII after being crosslinked by molecules other than antigen (question 3). MHCⅱⅱ molecules are mainly expressed in professional antigen presenting cells such as DC, monocyte macrophage and B lymphocyte, which are the main sensing cells for dangerous signals such as foreign pathogen components. Studies have shown that MHCⅱⅱ class ⅱ molecules can mediate reverse signals and affect and regulate many physiological processes of immune cells. Based on this, it is not clear whether MHCⅱⅱ class II molecules can induce danger signals or regulate immune responses triggered by danger signals (Question 4). We systematically studied the above four scientific problems and their possible internal relations, and discussed the interaction between CaMKII, miRNA targeting CaMKII and MHCⅱ class II molecules from four aspects, as well as the regulation and mechanism of natural immune response between macrophages and dendritic cells triggered by TLR. Regulation of 1. Ca/calmodulin-dependent protein kinase Ⅱ on natural immune response of macrophages induced by TLR and its mechanism. In the research of master's thesis, we found that LPS, CpG ODN and Poly (I: C) (TLR4, TLR9 and TLR3 ligands, respectively) can significantly induce the activation of CaMKlI, which is manifested by the increase of phosphorylation of CaMKII(T286) and the increase of kinase activity. At the same time, the inhibition of CaMKII activity by KN62, a specific inhibitor of CaMKII, can significantly reduce the production of inflammatory cytokines IL-6, TNF-α and IFN-β induced by TLR4, 9 and 3 ligands, and its downstream signaling mechanism is mediated by inhibition of MAPK, NF-κB and IRF3. To sum up, TLR ligand can induce macrophages to release intracellular calcium and activate CaMKII. Activated CaMKII can directly bind, phosphorylate and activate TAK 1 and IRF3, which are important signal molecules in TLR signal, thus enhancing the activation of downstream signal pathways, thus enhancing the production of inflammatory cytokines IL-6, TNF-α and type I interferon induced by TLR ligands, indicating the Ca2+/CaMKII signal pathway and TLR. This part of the study found the new immunomodulatory function of CaMKII and its target molecules, and also enriched the research content of TLR signal transduction regulation, which is helpful to further understand the immune response and its fine regulation mechanism when the body resists foreign pathogens. Second, the effect of miR- 148/ 152 targeting CaMKII on the maturation and function of dendritic cells. The maturation and activation of DC are the important basis of initial immune response and acquired immune response, and many regulatory factors are involved in maintaining the steady state of DC. Previous studies have shown that CaMKII is also an important regulator of DC maturity and function. Inhibition of CaMKII activation can down-regulate the expression of MHCⅱⅱ molecules on DC surface, the secretion of IL- 12 and IFN-γ, and the proliferation of CD4+T cells. Our previous studies have shown that CaMKII can enhance the production of inflammatory cytokines IL-6, TNF-α and type I interferon induced by TLR ligands. Since DC also expresses CaMKII, the TLR signal of DC should also be actively regulated by CaMKII. To sum up, miR- 148/ 152 negatively regulates the initial immune response and antigen presentation function of DC triggered by TLR ligand by acting on the target molecule CaMKII-α. MiR- 148/ 152 is a new negative regulator of DC maturation and function, which provides another new way for the regulation of immune response. Third, the mutual regulation between Ca2+/CaMKII and MHC Ⅱ Ⅱ molecules Previous studies have shown that antigen stimulation can induce the increase of intracellular calcium flow in DC, and the up-regulated calcium signal is an important factor needed for DC to mature and function. CaMKII can regulate the expression of DC MHCⅱ molecules, and inhibiting the activation of CaMKII can not only increase the lysosomal transport and degradation of MHC ⅱ molecules, but also inhibit the transcription and stability of MHCⅱmRNA. However, the cytoplasmic calcium flow and the activation of CaMKII caused by the cross-linking of MHCⅱⅱ molecules by molecules other than antigens are still unclear. We found that reducing the expression of DC CaMKII by siRNA can significantly inhibit the up-regulation of MHC class II molecules on DC surface induced by LPS, while cross-linking MHC class II molecules on DC surface with antibodies can enhance the activation of LPS-induced and uninduced CaMKII. Fourthly, the reverse signal of MHCⅱ class ⅱ molecules promotes TLR to trigger the natural immune response between macrophages and dendritic cells and its mechanism. At present, there is little research on the non-classical function of MHCⅱ class ⅱ molecules. Since MHC class II molecules and TLR are mainly expressed in professional antigen presenting cells, can we imagine whether MHC class II molecules can induce or assist the perception of danger signals or regulate the immune response stimulated by danger signals? We studied this problem by using gene knockout mice and RNA interference technology. Compared with wild-type mice (MHCⅱ+/+/+), DC derived from peritoneal macrophages and bone marrow in MHCⅱ-/- deficient mice significantly decreased IL-6, TNF-α, IL- 12 and IFN-β after being stimulated by LPS, CpG ODN and Poly (I: C). After interfering with the expression of MHCⅱ molecules in macrophages and DC, the secretion of cytokines induced by TLR ligands also decreased significantly. In a word, we studied the interaction between CaMKIIi α and MHC Ⅱ molecules targeted by camkiii, miR- 148/ 152, and their regulation on TLR signal transduction and related mechanisms, which proved that camkii and MHC Ⅱ molecules are necessary for antigen presenting cells-macrophages and DC TLR signals to be fully activated. At the same time, we found a new mirna (mir-148/152) that can regulate the maturation and function of DC, revealing that CaMKII and MHC Ⅱ Ⅱ can regulate each other in two main antigen presenting cells-macrophages and DC, thus * * * participates in maintaining the balance and stability of the immune system. The results of this study broaden people's understanding of the nature and function of MHCⅱⅱ class ⅱ molecules, enrich the research content of TLR immune recognition and its regulatory mechanism, and are expected to provide new enlightenment for the pathogenesis and treatment of immune-related diseases.