the below examples are exemplary , they are only used for illustrating the invention , and should not be construed as a limitation of the invention . it should be indicated that , without departing the principle of the invention , a person skilled in the art can make several modifications , which also fall within the protection scope of the invention . example 1 : construction of an expression vector containing the fusion protein experiment materials : t4 dna ligase ; vector pcdna3 . 1 ; competent bacteria jm109 ; plasmid extraction reagents ; pcr reagents . methods and results : based on the sequences of human tim - 3 gene fragment and human igg1 gene fragment disclosed in genebank , human tim - 3 - ig gene containing a proper linking sequence was prepared via artificial synthesis . the human tim - 3 - ig gene was mixed with a vector by a proper ratio in t4 dna ligase buffer , 0 . 5 u of t4 dna ligase was added , and ligation was performed at 16 ° c . overnight . 104 , of the ligation liquid was taken , added into 200 μl of competent bacteria jm109 and mixed gently . the mixture was subjected to ice bath for 30 min and 42 ° c . water bath for heat shock for 90 seconds , and then rapidly moved into ice bath for 2 min . 800 μl of lb medium was added to the mixture , and it was placed on a 37 ° c . constant temperature shaker with a shaking rate of 150 r / min for 45 min . after 4000 r / min centrifugation for 1 min , 800 μl supernatant was discarded , and the pellet was taken and spread on a solid lb plate containing amp ( final concentration 100 μg / ml ). the plate was placed upside - down in a 37 ° c . oven for 12 - 18 h . single clones were picked from the plate and inoculated in a lb medium containing ampicillin ( 100 g / ml ). the lb medium was placed on a 37 ° c . constant temperature shaker with a shaking rate of 170 r / min for overnight . 3 ml of bacterial liquids were respectively taken and added into 1 . 5 ml eppendorf tubes , which were centrifuged at 10000 r / min for 1 min , and the supernatant was discarded . using a plasmid extraction kit , the bacteria pellet was resuspended in 100 μl solution i , then 200 μl of freshly prepared solution ii was added , and it was gently reversed upside - down for several times until the liquid became clear . subsequently , 150 μl of solution iii was added , and the liquid was gently reversed upside - down for several times until it was evenly mixed ( a great deal of white flocculent precipitate appeared ). after centrifugation at 4 ° c . and 12000 r / min for 5 min , the supernatant was taken and added into another eppendorf tube , and equal volume of tris - hcl saturated phenol was added . after thorough shaking and centrifugation at 12000 r / min for 5 min , the upper aqueous phase was transferred to a new tube . 500 μl of chloroform was then added , and the extraction was performed once again . subsequently , the upper aqueous phase was carefully taken , and transferred into a new tube . 2 times of volume of absolute alcohol was added to the tube , mixed evenly , and placed at − 20 ° c . for 3 h . after centrifugation at 4 ° c . and 12000 r / min for 10 min , the supernatant was discarded , and the pellet was washed with 70 % alcohol twice , and then dried at room temperature for 20 min . the pellet was reconstituted with 40 μl sterile double distilled water , and then pcr identification and dna sequencing analysis were performed . the results indicated that human tim - 3 - ig gene was successfully cloned into the expression vector pcdna3 . 1 , and the vector plasmid containing the target gene was named as pcdna3 . 1 - tim - 3 - ig ( the sequence of tim - 3 - ig gene can be seen in seq id no . 2 ). example 2 : the expression of fusion protein and western blot assay protein lysate ; sds - page reagents ; tim - 3 antibody ( abcam company ); nc film ; chinese hamster ovary cell ( cho cell ); protein a sepharose cl 4b column ( beijing vector gene technology co . ltd . ); 20 % fetal bovine serum ( beijing yuanheng shengma biology technology research institute ); serum - free rpmi 1640 ( gibco company ). 1 ) the expression of the fusion protein : the recombinant plasmid pcdna3 . 1 - tim - 3 - ig prepared in the example was transfected into cho cells , which were cultured for several days , and then the supernatant was collected . 1 ml of 0 . 1 mol / l phosphate buffer ( ph 8 . 0 ) was added to the supernatant , and the ph was adjusted to 9 . 0 with 1 mol / l tris - hcl . the cell supernatant was loaded into a protein a sepharose cl 4b protein column ( well equilibrated with ph 8 . 0 , 0 . 1 mol / l phosphate buffer ), and the column was washed with the above buffer until no contaminant protein can be detected in the elute . citrate buffer ( ph 3 . 0 ) was used for elution , and the elute was collected and immediately neutralized using 1 mol / l tris - hcl buffer ( ph 8 . 5 ), and then dialyzed using 0 . 01 mol / l pbs ( ph 7 . 2 ) for 72 h . product was taken to measure od260 and od280 in a uv - spectrophotometer , so as to calculate the content of the protein ; the product was lyophilized and then stored at − 20 ° c . 2 ) the western blot assay of the fusion protein : the product of the tim - 3 - ig fusion protein was collected for measuring protein concentration . sds - page gel was prepared , and then electrophoresis , membrane transfer , and blocking were conducted . anti - human tim - 3 antibody was used for primary antibody incubation , secondary antibody incubation , and protein assay . the control protein in the experiment was ig . as shown in fig1 , tim - 3 - ig fusion protein can be specifically recognized by the anti - human tim - 3 antibody . example 3 : elisa assay for the binding activity of the fusion protein experiment controls : negative control ( merely containing the ig of the invention ), control 1 ( referred to as d1 protein with the sequence of seq id no . 3 ), control 2 ( referred to as d2 protein with the sequence of seq id no . 4 ), control 3 ( referred to as d3 protein with the sequence of seq id no . 5 ), and control 4 ( referred to as d4 protein with the sequence of seq id no . 6 ). methods and results : after the fusion protein was prepared , binding trials were used in the invention to measure the binding activity between the tim - 3 - ig fusion protein and gal - 9 . negative control , control 1 , control 2 , control 3 , and control 4 were also used . specific procedures were as follows : 1 ) gal - 9 protein coating : gal - 9 protein with the concentration of 1 - 10m / ml in buffer was used to coat the wells of a pvc microtiter plate , and an adhesive plastic sheet was used to cover the microtiter plate . the plate was incubated at 4 ° c . overnight . the coating solution was discarded , and the microtiter plate was washed twice by adding 200 μl pbs into the wells each time and gently shaking the microtiter plate ; 2 ) blocking and loading : 200 μl blocking buffer ( 5 % skimmed milk powder / pbs ) was added to each well , so as to block and coat the remaining protein binding sites in the wells , and an adhesive plastic sheet was used to cover the microtiter plate . the plate was incubated at room temperature for at least 1 - 2 h . 100 μl of properly diluted tim - 3 - ig fusion protein or control protein was added to each well , and incubated at 37 ° c . for 90 min ; 3 ) incubation with anti - tim - 3 antibody : 100 μl of diluted anti - tim - 3 antibody was added into each well , and an adhesive plastic sheet was used to cover the microtiter plate . the plate was incubated at room temperature for 2 h , and the microtiter plate was washed using pbs for four times . 100 μl secondary antibody was added , which had been diluted to optimal concentration in the blocking buffer prior to use , and an adhesive plastic sheet was used to cover the microtiter plate . the plate was incubated at room temperature for 1 - 2 h , and then washed by pbs for four times ; and 4 ) detection : 100 μl substrate was added to each well and developed for 30 min . the data were read immediately at 405 - 410 nm . the elisa results showed that , as compared to the controls , the tim - 3 - ig fusion protein of the invention had better binding effects with gal - 9 . example 4 : the blocking activity of human tim - 3 - ig fusion protein on human mononuclear cell line thp - 1 tim - 3 - ig fusion protein ( with the concentration of 5 μg / ml and 20 μg / ml , respectively ) and the negative control protein ig ( with the concentration of 5 μg / ml and 20 μg / ml , respectively ) were co - cultured with human mononuclear cell thp - 1 , respectively . the secretion level of il - 8 in the supernatant of each group was detected after 48 h . as shown in fig2 , the tim - 3 - ig fusion protein can up - regulate the expression level of il - 8 in a dosage - dependent way . example 5 : the blocking activity of human tim - 3 - ig fusion protein on human macrophage cell line u937 tim - 3 - ig fusion protein ( with the concentration of 5 μg / ml and 20 μg / ml , respectively ) and the negative control protein ig ( with the concentration of 5 μg / ml and 20 μg / ml , respectively ) were co - cultured with human macrophage u937 , respectively . the secretion level of il - 8 in the supernatant of each group was detected after 48 h . as shown in fig3 , the tim - 3 - ig fusion protein can up - regulate the expression level of il - 8 in a dosage - dependent way . example 6 : the blocking activity of human tim - 3 - ig fusion protein on human peripheral blood isolated human peripheral blood ( pbmc ) was co - cultured with tim - 3 - ig ( with the concentration of 10 μg / ml and 20 μg / ml , respectively ), negative control protein ig ( with the concentration of 10 μg / ml and 20 μg / ml , respectively ), and blank control , respectively . cd3 and cd28 were also used to stimulate cell proliferation . the supernatant was collected , and the expression of cytokine il - 6 was measured after 48 h . as shown in fig4 , the tim - 3 - ig fusion protein can significantly enhance the expression of il - 6 in pbmc . example 7 : the effects of human tim - 3 - ig fusion protein on the growth of tumor in tumor bearing mice ct - 26 tumor cells were first inoculated into the backside of balb / c mice , and different dosages ( 200 μg and 500 μg ) of tim - 3 - ig protein or the control protein ig ( 200 μg ) was simultaneously inoculated . two weeks later , the changes in the size of tumor were monitored , and the size of tumor was measured on day 14 , 16 , 18 , 20 , 22 , 24 , 26 , 28 , 30 , and 32 , respectively . the results were shown in fig5 . as compared to the control , tim3 - ig fusion protein can significantly inhibit the growth of tumor , and the inhibition effect of the tim3 - ig fusion protein was dosage - dependent . example 8 : the effects of human tim - 3 - ig fusion protein on the immunological functions in tumor bearing mice in example 7 , spleen cells of the mice were collected at 38 days after the treatment of the tim - 3 - ig on tumor bearing mice . pcr method was used to detect the expressions of the cytokines ifn - γ and tnf - α in each group . the results were shown in fig5 . as compared to the control , tim3 - ig fusion protein treatment can significantly increase the expression of immuno - cytokine , and the treatment of the tim3 - ig fusion protein was dosage - dependent . the present invention further provides a preparation containing tim - 3 - ig fusion protein . formulation : tim - 3 - ig fusion protein 20 mg / ml ; sucrose 37 mg / ml ; sodium phosphate 0 . 35 mg / ml ; tween - 200 . 1 mg / ml ; sodium chloride 4 mg / ml . the stock solution of the tim - 3 - ig fusion protein was obtained , and the concentration of tim - 3 - ig fusion protein should be higher than 20 mg / ml . formulation preparation : the required amounts of sucrose and tween - 20 ( final concentration as 37 mg / ml and 0 . 1 mg / ml respectively ) were calculated based on the volume of the stock solution , and then added into the stock solution . the concentrations of all the components in the solution were adjusted in accordance to the formulation , so as to obtain semi - finished products . the semi - finished products were sterilely divided into cillin bottles , which were capped with rubber plugs , lyophilized , and then capped with aluminum - plastic covers , so as to obtain the final products . in the above examples , in vitro experimental results indicated that tim - 3 - ig fusion protein can enhance the activation of human mononuclear macrophage ( u937 , thp - 1 ) and human peripheral blood mononuclear cell ( pbmc ); and in vivo experimental results indicated that the fusion protein can enhance the immunological responses in tumor bearing mice by blocking the immunosuppressive functions of tim - 3 , and inhibit the growth of tumor in a dosage - dependent way .
the present invention provides a human tim - 3 - ig fusion protein which can block tim - 3 signal pathway , and said ig fusion protein comprises tim - 3 protein , human ig fragment , and the linking sequence therebetween . in the present invention , a human tim - 3 - ig gene is obtained by an artificial synthesis process ; an expression vector containing the tim - 3 - ig gene is constructed ; and the prepared ig fusion protein is tested in an expression verification experiment , a binding activity experiment , a blocking activity experiment in different cell lines , and in vivo experiments in mice . the human tim - 3 - ig fusion protein prepared in the present invention can be used to treat immunological diseases caused by high expression of tim - 3 .