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SUMMARY The conventional method of assessing the platelet response to hypotonic stress (HSR) was adapted to allow microtitre plate technology to be used. After water is added to a platelet suspension two sequential readings are taken at 414 nM on a vertical microplate reader. The difference between the second (three minutes) and the first (one minute) was defined as the HSR. This method allowed the relation between platelet concentrate pH and viability to be confirmed, and an HSR value for use in quality control was established. The method correlated well with the conventional technique and permitted measurement of undiluted samples as well as of products with a high free haemoglobin concentration.After exposure to hypotonic stress platelets swell and then contract to their normal shape. This recovery phase requires the integrity of the platelet's biochemical functions and has been related to platelet viability as the hypotonic shock response (HSR). ' Many blood banks use the test as a measure of the quality of platelet concentrate, but the conventional spectrophotometers used to monitor the response are not part of standard blood bank equipment. Furthermore, the test is rather lengthy to perform and its use in testing large numbers of samples is thus limited. Microtitre plate tests are fast becoming part of standard blood bank methodology used in red cell grouping and virological screening. We therefore attempted to adapt our standard method for performing the platelet HSR to a microtitre plate format, in order to be able to a test a large number of samples on a vertical microplate reader. Material and methodsPlatelet concentrates were prepared in the components laboratory of the blood processing department of the Red Cross Blood Bank, using standard methods. Briefly, whole blood donations collected in CPD anticoagulant were centrifuged at 1375 x g for five and a half minutes and the platelet-rich plasma was siphoned into a satellite pack. An additive solution (100 ml) was added to the red cell pack which was then sealed. The empty additive pack then served as a container for platelet-poor plasma generated by centrifuging the platelet-rich plasma at 4000 x g for 12 minutes. The sedimented platelets were allowed to rest Accepted for publication 12 June 1989 for 90 minutes without agitation and were then resuspended on a horizontal agitator. Concentrates were resuspended in about 60 ml ofplasma at a platelet concentration of 4 -16 x 100"/1. Platelet concentrates were stored with continuous agitation for five days at a controlled temperature of -20-240C.To prevent contamination samples were taken from concentrates by stripping down integral protions of plastic tubing into the pack, allowing platelet suspension to fill the tubing and sealing off a segment using a heat sealer.

Background: Tisagenlecleucel (Tisagen) and Axicabtagene Ciloleucel (Axicel) CD19 CAR T-cell products are licensed in the UK for adults with relapsed/refractory high-grade B-cell Non-Hodgkin's lymphoma (B-NHL). Infection rates for the first 30 days post CAR T range from 23% (Hill et al, Blood 2018) to 42% (Park et al, Clin Infect Dis 2018) with a predominance of early bacterial infections. Infection etiology is multifactorial, including pre-existing immunosuppression, poor marrow reserve, concomitant disease, delayed cytopenias and lymphodepletion. CRS has been shown to be an independent risk factor and associated treatment (Tocilizumab, steroids) may contribute. Risk assessment is limited by heterogenous cohorts in published reports and practice variations in use of prophylactic antibiotics and intravenous immunoglobulin (IVIG). To determine incidence and outcome of infection with licensed CAR T-cell products, we conducted a retrospective review at UCLH, London, UK. Methods: Electronic medical records were used to collect data on patients treated with Tisagen/Axicel from May 2019 to July 2020. Infections at ≤28 days and >28days following infusion were recorded. Infections were defined as a positive microbiological/virology result in conjunction with clinical symptoms. Invasive fungal infections were classified according to revised EORTC criteria. Infections were graded as severe (requiring systemic treatment) or life threatening (hypotension/organ support). Results: Sixty adults with B-NHL received Tisagen (n=19) or Axicel (n=41). Patients did not receive prophylactic antibiotics. IVIG was given for hypogammaglobulinaemia with recurrent infections (n=4). Within 28 days of infusion, 44 episodes of infection occurred in 28 patients (47%). Post day 28 (range 29-452), 19 episodes occurred in 9 patients (15%). Severe (n=9) and life-threatening (n=7) infection occurred in 15% and 12% of patients respectively, with two infections resulting or contributing to death (3.3%). Infections were bacterial (56%), respiratory viral (24%), other viral (14%) and fungal (6%). Six (10%) developed viral reactivations; CMV (n=1), BK virus in blood or urine (n=2), HHV6 (n=1) or AdV (n=2). PCR proven JC virus causing progressive multifocal leukoencephalopathy was reported in 1 patient at day 116. Only one late COVID-19 infection occurred despite the program remaining operational throughout lockdown. There was no association between early infection and CRS severity (p=0.43), or use (p=0.94) and dose of Tocilizumab (p=0.54). With regard to pre-treatment variables, advanced disease at time of infusion (≥stage 3) was associated with higher risk of any infection (OR 4.2, 95% CI 1.3- 13.4, p=0.016) and lines of prior therapy (≥3) with higher risk of early infection (OR 3.0, 95% CI 1.0-8.9, p=0.048). Steroid treatment was associated with a higher risk of early (and overall) infection (OR 3.0. 95% CI 1.0-8.6, p=0.048). A diagnosis of ICANS was associated with infection beyond day 30 (p=0.021). In multivariate analyses, steroid use (p=0.03) and ≥3 lines of prior therapy (p=0.021) were associated with infection ≤28 days of infusion. Steroid use (p= 0.049) and stage pre infusion (p=0.023) were associated with higher risk of any infection. Conclusion: In this real world analysis of B-NHL patients treated with Tisagen or Axicel, 47% developed early infection at ≤28 days. Severe or life-threatening infection occurred in 27% of patients. Multivariate analysis confirms significant association with (1) steroid exposure (2) ≥stage 3 disease and (3) ≥3 lines of previous therapy. There was no overt association with Tocilizumab use or CRS severity. Unlike other centers, our cohort did not receive prophylactic antibiotics or IVIG. Patients with advanced disease are high risk for CRS, ICANS and infectious complications. Risk modification strategies include bridging optimization to reduce disease burden pre CAR T with infectious prophylaxis from referral until at least 3-6 months post-infusion. In this analysis, steroids represent a significant risk and efforts should be made to wean doses swiftly. The use of steroid sparing agents such as Anakinra may be important (clinical trial results awaited). In ≥ stage 3 disease or heavily pre-treated patients, there may be a role for prophylactic antibiotics but this should be explored within a clinical study with consideration of local antimicrobial resistance patterns. Disclosures Neill: Novartis: Other: Funded attendance at academic conferences; Celgene: Other: Funded attendance at academic conferences. Townsend:Roche, Gilead: Consultancy, Honoraria. Ardeshna:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi, Genzyme, AstraZeneca: Speakers Bureau; University College London (UCL)/UCL Hospitals (UCLH) Biomedical Research Unit: Other: Supported by this organisation. Cwynarski:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Atara: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support. Peggs:Autolus: Consultancy. Roddie:Celgene: Honoraria; Gilead: Honoraria; Novartis: Honoraria. O'Reilly:Gilead: Honoraria; Novartis: Honoraria, Other: Travel support.

The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

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