New Model of Splenocyte Transfer Exacerbates Salt‐Sensitive Renal Injury and Hypertension in Rats
Authors: Fehrenbach Daniel J. , Dasinger John Henry , Lund Hayley , Zemaj Jeylan , Mattson David L. 
Published: April 2020

Infiltration of immune cells into target organs, including the kidney, is a hallmark of hypertensive pathology, driving the use of various experimental manipulations to interrogate the influence of the immune system. Previous studies using RAG1−/− Dahl Salt‐Sensitive (SS) rats demonstrated that the adaptive immune system plays a vital role in potentiating the hypertensive phenotype. More specifically, we created a line of Dahl SS rats with a null mutation in the CD247 gene. CD3+ T cells are absent in these SSCD247−/− rats, but a B cell population is preserved. Compared to SS rats, we observe an attenuation in renal injury in SSCD247−/− rats when subjected to a high salt (HS) challenge (−109mg/day albuminuria), mirroring an attenuation in hypertension (−19mmHg). Though adoptive transfer studies are useful in mice models of hypertension, there has yet to be a study to demonstrate adoptive transfer of immune cells potentiating a genetic model of SS hypertension. Using the male T cell deficient Dahl SS rat, SSCD247−/−, we hypothesized that splenocyte transfer from SS wildtype rats into SSCD247−/− rats would populate the T cell compartment and exacerbate the SS phenotypes. Furthermore, we tested the hypothesis that splenocytes from high‐salt fed donors (HSS) would induce a more dramatic salt‐sensitive phenotype in the recipients than donors fed a low‐salt diet (LSS). The splenocyte transfer recipients (n=11/13) were compared to naïve SSCD247−/− rats (n=7). As engraftment of adoptively transferred cells is difficult to achieve reliably, we present a new approach demonstrating that transfer of splenocytes from adult rats into recipient pups at postnatal day 5 is feasible for robust population of the T cell compartment in the circulation and spleen. Using flow cytometry, greater than 80% of the constituted CD3+ T cells were CD4+ Helper T cells. In comparison to SSCD247−/− T cell deficient rats, by HS day 21, recipients receiving splenocyte transfer from both low‐salt and high‐salt fed donors showed an exacerbated rise in SS blood pressure (LSS, 150.3±19.0mHg; HSS, 155.2+/−20.8mmHg; vs SSCD24−/− 135.6±2.9mmHg; p<0.01) negating the effect originally observed in the knockout (+15–20mmHg). No difference was observed between LSS and HSS recipients. Mirroring the blood pressure, rats receiving the transfer developed greater renal damage assessed by albuminuria (+140mg/day, p<0.001) and outer medullary protein casting (p<0.05). To determine whether T cells contributed to the renal damage observed, we used flow cytometry to assess renal immune cell infiltration. Not only were the transferred cells able to infiltrate into the kidney, these T cells were more than 92% CD4+ cells. Not one phenotype showed any significant difference between those receiving splenocytes from low‐salt or high‐salt fed donors. These studies provide the first evidence that genetic salt‐sensitivity can be enhanced using adoptive immune cell transfer. Furthermore, we have documented that CD4+ cells infiltrate into the kidney which is accompanied by increased renal damage. Lastly, we note that the amount of salt in the diet of the donors does not affect the SS phenotypes of the recipients.

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F31HL144084, HL116264, and HL137748