Four-month-old female NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mouse, (Mus musculus).Animal presented moribund after receiving a xenotransplant.

Gross Description:  

Discolored nodules were visible on the kidney.  Secondary lymphoid tissues were markedly reduced in size consistent with the phenotype of the strain.

Histopathologic Description:

There is marked, multifocal to coalescing neutro-philic inflammation and necrosis arranged in an embolic pattern and which distorts the overall structure of the kidneys as viewed subgrossly.  Inflammation is centered on 0.5um wide X 8.0-10.0uM long fungal organisms that form non-branching hyphae and pseudohyphae.  Organisms and the accompanying inflammatory response involve predominately vascular and perivascular, interstitial spaces and the tubules with limited extension into the kidney parenchyma.  Affected renal tubules are variably ectatic and contain combinations of serocellular debris and acellular eosinophilic material.  The renal interstitium is variably expanded by inflammation and reactive fibroblasts, especially where inflammation is present.  The adjacent sections of liver are unremarkable. Yeast forms are also observed in the following locations: Both ears, heart, and the stomach.

Morphologic Diagnosis:  

Kidney:  Tubulointerstitial nephritis, suppurative, bilateral, acute, severe with intratubular fungal organisms most consistent morphologically with Candida albicans.

Lab Results:  

Microbiology, Aerobic bacterial culture of both tympanic bullae:  Klebsiella pneumonia. Microbiology, Aerobic bacterial culture of blood:  Staphylococcus xylosus.


Systemic candidiasis

Contributor Comment:  

Non-obese diabetic (NOD)/severe combined immune deficiency (SCID)/IL2rγnull (NSG) mice represent a severely immunocompromised mouse strain that is an important tool for xenotransplantation studies using patient-derived tissues.  This strain is deficient in mature B cells, mature T cells, and natural killer (NK) cells.  Additionally, macrophages and dendritic cells are defective regarding their functions.5 While the severe immunodeficiency trait of the strain is useful for avoiding immune-mediated host rejection of foreign cells, this compromised status leaves NSG mice susceptible to a number of opportunistic pathogens.  Three commonly encountered opportunistic pathogens of immuno-compromised laboratory mice are either observed in tissue lesions or are isolated from body fluids of this NSG mouse including Candida albicans, K. pneumoniae and S. xylosus.

Candida albicans , the organism observed in the renal lesions, is a common microbial component of the gastrointestinal tracts of mice and other species that is held in check by aspects of both the innate and adaptive immune responses.3 The ability of different laboratory mouse strains and man to contain any disease that may be induced by C. albicans is often related to having the appropriate T-cell-directed phagocytic responses.1  Interestingly the depletion of T lymphocytes in the human and mouse generally results only in a severe mucosal overgrowth of this yeast. Furthermore, neither nude nor NOD-SCID mice have shown increased susceptibilities to developing systemic candidiasis, which indicate that the innate immune system offers protection, as well.1 However, impaired NK cell function appears to be essential for immune-mediated signaling that shields against developing systemic candidiasis.  Therefore, severely immuno-suppressed hosts, such as the NSG mouse, are uniquely susceptible to systemic disease induced by C. albicans infection.4

JPC Diagnosis:  

1. Kidney: Pyelonephritis, suppurative, acute, multifocal, marked with pseudohyphae and yeast, NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mouse, Mus musculus.

2. Liver: No significant lesions

Conference Comment:  

In addition to being globally immuno-deficient and uniquely susceptible to a variety of opportunistic infections, non-obese diabetic (NOD)/severe combined immune deficiency (SCID; NSG) mice are selectively bred as an animal model for type I diabetes mellitus (DM) in humans.3 In NOD mice, DM develops as a result of spontaneously developing autoimmune insulitis in the pancreatic islets cells. The onset of DM is associated with a moderate glycosuria and a non-fasting hyperglycemia, which may be important for the proposed pathogenesis of this lesion discussed below.3 As mentioned by the contributor, NOD-SCID mice have functional defects in macrophages, dendritic cells, natural killer (NK) cells, NKT cells, regulatory CD4+CD25+ cells, and are C5a deficient. The susceptibility of these mice to develop DM is much higher in a sterile environment.3

Virulence of C. albicans is dependent on adherence of the organism to mucosal epithelial cells mediated by its virulence factor, adhesin. The important components of adhesins are agglutinin-like sequence (ALS) proteins and hypha-associated GPI-linked protein (Hwp1).6,7 Superficial (localized) candidiasis produces relatively mild lesions in skin and mucous membranes while systemic (disseminated) candidiasis may involve any organ with the kidneys, heart valves, CNS and lungs most commonly affected. Immunosuppression, cytotoxic chemotherapy, diabetes mellitus, long-term glucocorticoid therapy, prolonged use of broad-spectrum antibiotics, or disruption of mucosal barriers predispose to infection. In addition, C. albicans can exist as yeast, pseudohyphae, or true hyphae depending on environmental conditions and temperature. This polymorphism enables C. albicans to infect a variety of tissues throughout the body.6,7 The yeast form has been implicated in disseminated systemic infection while hyphae and pseudohyphae have stronger adherence and invasiveness due to the expression of ALS adhesins, catalases, and protein hydrolases, such as secreted aspartyl proteinases (SAP), which also supply the pathogen nutrients through protein degradation.6,7

Conference participants noted large numbers of Candida sp. pseudohyphae and yeast admixed with and surrounded by suppurative inflammation in the renal pelvis as well as filling and expanding renal tubules in both the cortex and medulla. Occasionally tubules rupture and the inflammation extends into the adjacent renal interstitium. Participants agreed that this pattern of inflammation is consistent with pyelonephritis and retrograde extension of exudate into the renal tubules and renal parenchyma. The most common cause of pyelonephritis is via ascending infection from the lower urinary tract.2 Opportunistic pathogens, such as Candida albicans, can commonly ascend into the kidney from the lower urinary tract, especially if there is glycosuria in a severely immuno-compromised and diabeteic animal. Females are predisposed to ascending urinary tract infections and pyelonephritis due to their relatively shortened urethra compared to males.2 Alternatively, hematogenous suppurative and embolic nephritis usually results in multiple microabscesses within the glomeruli, multifocal vascultitis, and hemorrhage within the medulla. In this case, conference participants noted perivascular in-flammation, but not significant vasculitis or glomerular lesions.2


1. Ashman, R, Farah, C, Wanasaengsakul, S, Hu, Y, Pang, G, Clancy, R.  Innate versus adaptive immunity in Candida albicans infection.  Immunol Cell Biol.  2004; 82(2):196-204.
2. Percy DH, Barthold SW. Pathology of Laboratory Rodents and Rabbits, 4th ed. Ames, IA: Blackwell Publishing; 2016:4,79.
3. Quintin J, Voigt J, Van der Voort R, et al. Differential role of NK cells against Candida albicans infection in immunocompetent or immunocompromised mice. Eur J Immunol. 2014; 44(8):2405-14.
4. "'>Shultz L, Yoriko S, Najima Y, et al.  Generation of functional human T-cell subsets with HLA-restricted immune responses in HLA class I expressing NOD/SCID/IL2rγnull humanized mice.  Proc Natl Acad Sci USA. 2010; 107:13022-13027.
5. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA:Elsevier; 2016:202.
6. Voon KC, Lee TY, Rusliza B, Chong PP. Dissecting Candida albicans infection from the perspective of C. albicans virulence and omics approaches on host-pathogen interaction: A review. Int J Mol Sci. 2016; 17:1643.

Click the slide to view.

2-1 Kidney and liver, NOD mouse.

2-2. Kidney, NOD mouse.

2-3 Kidney, NOD mouse.

2-4. Kidney, NOD mouse.

2-5. Kidney, NOD mouse.

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