TABLE 2.

Commonly utilized major immune‐compromised mouse strains and their advantages and disadvantages

Sr no	Advantages	Disadvantages	Ref.
Nu/nu (Nude mouse)	First immunodeficient mouse strain The total number of circulating lymphocytes is five to six times less in nude mice than in normal animals. The majority of these cells are B cells so they are used for numerous cancer metabolomics research Highly correct prediction rates in comparison to in vitro systems for resistance and sensitivity of a tumor	A significant limiting factor is the duration of testing because a time of at least 4 months is required for rapidly growing tumors and two years are required for slowly growing tumors after that test results can be obtained Nude mice are expensive they need special conditions behind laminar flow barriers to avoid infections	31, 32
Severe combined immunodeficiency syndrome (SCID)	No mature B and T cells and decreased NK activity Provide realistic heterogeneity of tumor cells It can predict the response of the drug of a tumor in human patients. It can allow the rapid analysis of human tumor response to a therapeutic regime	Since they are immunocompromised, they provide a less realistic tumor microenvironment They are expensive and technically complicated Low level of engraftment of human cells They have a very short life span of approximately 8.5 mo	34, 35
Nonobese diabetic (NOD)‐SCID gamma (NSG)	Easy to prepare NSG mice live longer than any other immune‐deficient mice Deficient in IL‐2 receptor gamma chain and lack of mature B, T, NK cells, and cytosolic signaling Used for metabolomics study for human immune deficiency virus	No primary immune response No multilineage hematopoiesis Expensive and technically complicated	36, 37
Recombination‐activating gene (Rag)	Similar to SCID mice possess RAG 1 or 2 mutations No mature B and T cells and radiation resistant	Surgical implantation is needed Human fetal tissue requirement Low or variable engraftment of human cells Might need additional conditioning to attenuate the primary immune response	36, 37, 39
NOD rag gamma (NRG)	It possesses RAG‐1 and IL‐2 receptor common gamma chain mutation NRG mice better tolerate irradiation allowing higher levels of human cord bloodstream cell engraftment than NSG mice NRG mice can prove useful for cell or tissue implantation studies	High engraftment levels of human cells in the newborn as compared to adults Xenospecific selection of human T cells might occur	36, 37, 40, 41