Table 1. A tabulated summary of the study characteristics.

Abbreviations – ACT: adoptive cellular transfer; ATCT: adoptive T-cell transfer; CTLA-4: cytotoxic T lymphocyte-associated protein 4; ICB: immune checkpoint blockade; MSCs: mesenchymal stem cells; OS: osteosarcoma; PD-1: programmed death cell receptor 1; TME: tumor microenvironment; YOP: year of publication.

Author	YOP	Journal	Country	Study type	Primary endpoints of the study
Wang et al. [12]	2016	Front Immunol	China	Review	T-cell-based treatments for OS, with a focus on combination methods to boost the efficacy of ATCT.
Lindsey et al. [7]	2017	Rheumatol Ther	USA	Review	Summarizes current knowledge of the genesis of OS, diagnostic techniques, and the current standard of treatment. Presents a range of experimental treatments, as well as data that support a prospective shift toward immunomodulation.
Rivera-Cruz et al. [13]	2017	Stem Cells	USA	Review	A discussion of the mechanisms by which MSCs are able to modulate the adaptive and innate immune responses, including the relationship between MSCs and immune cells within the TME.
Nathenson et al. [14]	2017	Oncologist	USA	Review	The author discusses the history of immunotherapy research in the treatment of soft tissue and bone sarcomas, as well as the current state of the field, with a focus on vaccination trials, ATCT, and immune checkpoint inhibition.
Grohar et al. [9]	2017	Am Soc of Clin Oncol	USA	Author manuscript	The clinical and demographic features in treatment for Ewing sarcoma and osteosarcoma, including the biology of the germline mutation.
Wedekind et al. [15]	2018	Paediatr Drugs	USA	Review	The current state of cancer immunotherapies, including effectiveness and toxicity in pediatric patients, as well as new prognostic biomarkers that might lead to individualized treatments.
Dyson et al. [10]	2019	J Hematology Oncol	USA	Review	Highlighting the TME and specific immunotherapeutic targets.
Miwa et al. [8]	2019	J Oncol	Japan	Review	The authors discuss immune surveillance for cancer, the history of immunotherapy, and the latest clinical studies on OS immunotherapy.
Jiang et al. [16]	2019	Cell Prolif	China	Review	Reviews the mechanisms regulating the immune modulation function of pro- and anti-inflammatory cells, with a focus on MSCs and their immunosuppressive effects.
Casey et al. [17]	2020	Cancer Immunol Res	USA	Author manuscript	Neoepitope expression and future advances of T-cell infiltration into the immunosuppressive TME.
Birdi et al. [18]	2020	J Immunother Cancer	Canada	Review	Highlights clinical data supporting how immunotherapy is being used in soft tissue sarcoma and bone sarcomas.
Zhang et al. [19]	2020	Medicine	China	Review and meta-analysis	The results of survival analysis of potential prognostic genes are significantly associated with childhood OS.
Clemente et al. [20]	2021	J Transl Med	Italy	Review	Gives insight on groundbreaking advances in the immune-therapeutic field, as well as the possible applications of immunological therapies in sarcomas, including ICB via modification of the axis in CTLA-4 and PD-1, plus therapies with ACT.
Dong et al. [21]	2021	Front Immunol	China	Review	Discusses immune cells in the TME and new immunotherapy strategies based on immune cell modulation.
Rathore et al. [2]	2021	J Clin Med	USA	Review	The biological mechanisms that contribute to tumor development are investigated, and this information is used to describe new therapy options for OS.
Gazouli et al. [22]	2021	Cancers	Greece	Review and meta-analysis	A detailed analysis of recurrent osteosarcoma treatment strategies over the last two decades. This report compares the current treatment strategies to the objective responses in potential therapies of preclinical and clinical trials.