# Skewed pretransplant lymphocytes subpopulations correlate with opportunistic infection onset within the first two years following kidney transplantation

## TL;DR

Higher levels of certain immune cells before kidney transplant are linked to a higher risk of infections in the first two years after surgery.

## Contribution

The study identifies pretransplant immune cell markers associated with opportunistic infections after kidney transplantation.

## Key findings

- Higher pretransplant NK cells and age-associated B cells correlate with opportunistic infections after kidney transplantation.
- Elevated NK cell counts before transplant remain a significant predictor of early opportunistic infections.
- No immune cell populations were linked to acute rejection after transplantation.

## Abstract

After kidney transplantation (KT), there is no reliable assessment of the immunosuppressive state. We analysed pre-KT T-, B- and NK-cell populations in relation to the occurrence of opportunistic infections (OI) or acute rejection (AR) after KT.

We included 422 adult KT recipients from 01/2016 to 09/2020. Immune cells were analysed using flow cytometry in 283 recipients before KT in three groups: AR, OI or no event within 24 months after KT.

There were 49 recipients in the OI group, 44 in the AR group and 190 in the control group. Before KT, higher absolute counts and percentages of NK cells (p=0.001 and p=0.007 respectively), elevated absolute counts of plasmablasts and CD21-CD38- B cells (age-associated B cells) (p=0.045 and p=0.028 respectively), and a lower proportion of CD3+ T cells (p=0.022) were independently associated with the occurrence of OI within two years following kidney transplantation (KT). In recipients with OI occurring before three months, only absolute count of NK cells before KT remained independently associated with the occurrence of OI (p=0.002). None of the studied immune cell population was associated with AR.

Our results suggest that higher levels of pretransplant NK cells and age-associated B cells are correlated with the occurrence of OI within two years after KT. This result may improve stratification of individualized infectious risk prior to KT.