*Purpose: Optimal dosing of thymoglobulin (ATG) for induction has not been well defined. Our protocol aims for 5-6mg/kg cumulative dose divided over 4 doses. However, it is unclear if lower dose ATG results in an increase in rejections (either subclinical or clinical TCMR or AMR) in the short term.

*Methods: Data collection was done through retrospective chart reviews of all patients who received a kidney transplant at our center between January 1, 2013 and December 31, 2017. Data collected included patient demographics, HLA mismatch, PRA, organ source, CIT, DSA, number and type of rejections, both subclinical and clinical, within the first 6 months post transplant. Patients who did not receive a biopsy within the first 6 months post transplant were excluded.

A total of 549 patients were divided into 2 groups; Grp 1 (n=60) those who received <5mg/kg ATG and Grp 2 (n=489) those who received >=5mg/kg. All rejections were biopsy proven and included both clinical and subclinical rejections. The Banff schema was followed for classification of rejections. Rejections were treated per center protocol.

*Results: Baseline characteristics were similar between groups except that Grp 2 had a greater proportion of patients with PRA>20. (Table 1). The vast majority of the rejections were T cell mediated (TCMR) and a small number were mixed. TCMR (Banff 1A or greater) was present in 37% of those who received <5mg/kg ATG vs 25% of those receiving >=5mg/kg (p=0.046). The odds of TCMR were 1.93(95% CI 1.08-3.5; p=0.027) times higher for those receiving <5mg/kg ATG compared with >=5mg/kg, independent of sex and PRA.

*Conclusions: Induction dose of ATG less than 5 mg/kg may be associated with a heightened risk of early rejections (subclinical or clinical) even in patients with low PRA.

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