1. Figure S1 b a c Supplement Figure 1. Basic functional characterization of B10G5 antibody. a. B10G5 neutralizing free sMICA in in vitro assay. Various concentration of B10G5 antibody was added to normal human serum containing a given amount (0.8 ng) of sMICA. Free sMICB in the serum was then measured with ELISA. Data shown that B10G5 neutralizing free sMICA. b. Histogram plots demonstrating that B10G5 binding to surface MICB overexpressed on TC2 cells. c. A standard 51 Cr-release NK cell cytotocixity assay demonstrating that B10G5 enhance NK cell killing of TC2-MICB cells. Data demonstrate the agonist nature of B10G5 in enhancing NK cell activity against TC2MICB cells. ng/ml TC2-MICB TC-MICB TC2 Specific Lysis (%) E:T

2. Figure S2 a b Serm level (pg/ml) Supplement Figure 2. Changes in serum levels of cytokines and chemokines with depletion of lymphocyte subsets during B10G5 therapy. (a) With CD4 depletion during B10G5 therapy (n>5 animals per group). (b) with NK depletion during B10G5 therapy (n>6 per group). Data show that serum cytokine “storm” in response to B10G5 therapy was an accumulative effect of activation of multiple cell types. Cytokine level was measured with multiplex assay by Eve Technologies.

3. Figure S3 a 6.77 4.89 NK1.1 14.1 3.09 spleen B10G5cIgG LN B10G5cIgG V 450 dilution b * B10G5cIgG Proliferation of CD45.1 + NK (spleen) * B10G5cIgG Proliferation of CD45.1 + NK (iymphonode) TRAMP/MIC mice Age 6 16 24 27 32 33 (wks) Tx (B10G5 or cIgG) i.v. injection of 5x10 5 V 450 -labeled congenic CD45.1 NK c Supplement Figure 3. Anti-sMIC mAb B10G5 therapy significantly increase homeostatic proliferation of adoptively transferred NK cells. (a) Depiction of the therapy and adoptive transfer of CD45.1 congenic NK cells. Five days before therapy study end point, mice (CD45.2) received i.v. injection of V 450 -labeled congenic CD45.1 NK cells (5x10 5 /mouse). (b) Representative graphs of flow cytometry analyses of V 450 -dilution of CD45.1 NK cells in the spleen and lymph nodes of mice in respective therapy groups. (c) Summary statistics of CD45.1 NK cell proliferation in the spleen and lymph nodes.

4. a PBMC 11.4 11.0 14.4 11.9 26.1 26.9 dLN B10G5cIgG 17.3 11.1 spleen B10G5cIgG dLN B10G5cIgG spleen B10G5cIgG B10G5cIgG CD3 CD4 b T-bet CD4 Figure S4 Supplemental Figure 4. B10G5 therapy did not impact CD4 T cell homeostasis but increased T-bet expression. 30.49.7

5. Figure S5 dLNspleenTIL CD8 TRAMP/MICB + B10G5 TRAMP/MICB + cIgG TRAMP Supplement Figure S5. Undetectable endogenous SV40TAg epitope I-specific CD8 T cells shown by lack of positive staining by H-2D b -restrcited TAg epitope I-specific tetramer (D b /I-Tetramer). D b /I-Tetramer

6. Figure S6 Tx (Day 20) * Days post tumor inoculation Tumor volume (mm 3 ) a e IFN  + CD8 T in the LN cIgGB10G5 * d BrdU + % NK (Spleen) cIgGB10G5 * BrdU + % NK (bone marrow) cIgGB10G5 * c NK% in LN cIgGB10G5 * NK% in splenocytes cIgGB10G5 * NK% in Tumor infiltrates * cIgGB10G5 f IFN  + CD4 T in the LN cIgGB10G5 * CD8 T % in Tumor infiltrates cIgGB10G5 * g Supplement Figure 6. Anti-sMIC mAb B10G5 therapy inhibits the growth of transplantable TRAMP-sMICB tumors. sMIC-expressing prostate tumor cell line TRAMP-C2 (designated as TRAMP-C2-sMICB) was implanted subcutaneously (s.c.) into syngeneic B6.MICB transgenic mice (5x10 5 cells/mouse). 20 days post-tumor inoculation, animals were randomized into two treatment groups (Tx, n=12 per group): control IgG (cIgG) or B10G5. Animals receive respective treatment i.p. twice weekly at the dose of 4 mg/Kg body weight. (a and b) Tumor growth curve (a) and Kaplan-Meier survival curve (b) demonstrating that B10G5 significantly inhibited tumor growth and increase survival. Survival end point defined as tumor volume reaches 1500 mm 3. (c) B10G5 therapy significantly increased NK cell frequency in the periphery. (d) B10G5 therapy significantly enhanced the ability of NK cell renewal in tumor host shown by marked increase in BrdU uptake. (e, f) B10G5 therapy significantly potentiated CD8 and CD4 T cell function as shown by IFN  production in response to PMA/ionomycin re- stimulation. (g, h) B10G5 therapy significantly increased cytotoxic NK and CD8 T cells to tumor parenchyma. Data in c-h were obtained from 6 animals from B10G5 or cIgG treatment group at day 8 after treatment initiation.. * p < 0.05. h b. Survival % P<0.01 days since Rx 010203040 0 50 100 B10G5 cIgG

7. H-2K b /OVA 257-264 tetramer CD8 B10G5cIgG a. TIL, gated on CD45 + CD3 + CD8 + 0.154.15 OVA 257-264 tetramer + (of CD8) B10G5 cIgG * 0.6 3.2 CD8 B10G5cIgG IFN  b. TIL, gated on CD45 + CD3 + CD8 + Figure S7 Supplement Figure 7. Anti-sMIC therapy enhanced antigen-specific CD8 T cell responses in the transplantable TRAMP-C2-sMICB-OVA tumor model. Although TRAMP-C2 (TC2) cell line was derived from tumors of TRAMP mice, SV40TAg was lost during. To address antigen-specific responses in the transplantable TC2-sMICB model, we overexpressed OVA in TC2-sMICB-TC2 cells. B10G5 therapeutic experiment was performed similarly to which in Supplement Figure 4. At the study end point, tumor infiltrated OVA peptide-specific CD8 T cells were detected with H-2Kb-restricted OVA257-264 tetramer (with H-2K b /OVA257-264 tetramer). (a) Frequency of H- 2K b /OVA257-264 tetramer + CD8 T cells in the tumor infiltrates (TILs). (b) Response of CD8 T cells in TILs to OVA257-264 peptide stimulation. Bulked tumor single cell suspension was re-stimulated with OVA257-264 peptide for 6h. IFN  +  of CD8 * B10G5 cIgG

8. Figure S8 Supplementary Figure 8. Therapeutic effect of B10G5 against well-differentiated TRAMP/MICB tumors. Cohorts of 20 week TRAMP/MIC were treated with B10G5 or cIgG (4.0 mg/KG BW) twice a week for an 8-week duration. a, prostate weight. b, Representative micrograph of tumor antigen SV40T staining showing micrometastatic deposits in the lung of animal in control group, but not in the B10G5 treated group. c-f, B10G5 therapy increases total splenic NK cell number (c), the ability of NK cell to self-renew (d), function of NK cell shown by increased IFNg production in response to PMA/I re-stimulation (e) and granzyme B production against TC2-MICB cells (f). g and h, B10G5 therapy potentiates CD8 T cell function and increases CD44 hi CD8 T cells in tumor-draining LN. i and j, B10G5 therapy potentiates CD4 T cells to Th1 responses and increases CD44 hi CD4 T cells in tumor-draining LN. All data were collected at study end point. *p < 0.05. **p<0.01. B10G5 IFN  + CD8 % (dLN) cIgG * CD44 hi CD8 % (dLN) cIgG * IFN  + CD4 % (dLN) cIgG B10G5 ** BrdU + NK % (spleen) cIgG ** Total splenic NK (X10 5 ) cIgG B10G5 ** Granzyme + NK % (spleen) cIgG B10G5 ** IFN  + NK % (spleen) cIgG B10G5 ** CD44 hi CD4 % (dLN) cIgG B10G5 * 0.0 0.5 1.0 1.5 2.0 2.5 Prostate Weight (g) cIgG B10G5 cIgG B10G5 SV40T a.b. c. d. e.f. g. h. i. j.

9. Figure S9 spleen LN T-bet CD4 29.215.4 20.013.8 Supplementary Figure S9. Representative flow cytometry analyses demonstrating that depletion of NK cells during B10G5 therapy impairs CD4 T cell Th1 responses. (a) Representative dot plot demonstrating that NK depletion during B10G5 therapy impairs CD4 T cell IFN  production in response to PMA and ionomycin re-stimulation. (b) Representative dot plots demonstrating that NK depletion during B10G5 therapy reduces transcriptional factor T-bet expression on CD4 T cells. a b spleen LN CD4 5.6 3.4 3.7 1.0 IFN  anti-MIC +  NK1.1 anti-MIC + mIgG anti-MIC +  NK1.1 anti-MIC + mIgG