This is a platelet transfusion study. The purpose of this study is to measure the life span and quality of platelets stored in a refrigerator. Participants will give platelets by apheresis. Platelets will be stored for 3 -20 days. A small portion of the subject's own stored platelets will be tagged with a radioactive isotope and infused back into the participant. This will enable us to track how many transfused platelets survive after storage in the refrigerator.

A single hyperconcentrated apheresis platelet unit will be collected from a healthy adult volunteer subject using the Trima Accel® Automated Blood Collection System. Concurrent plasma will be collected. The platelet unit will be stored, not-agitated, for up to 20 days at 4°C in a suspension of 35% plasma and 65% PAS (Platelet Additive Solution).

At the end of the storage period, the subject will return to receive an 111Indium Oxine (Indium 111, In-111) radiolabeled aliquot of their 4°C stored platelets. Follow-up samples from the subject will be collected approximately 2 hours post-infusion and on Days 1 (2X), 2 (2X), and 3 to calculate recovery and survival of the subject's 4°C stored platelets. The Day 1 and Day 2 the sample draws will be 2 - 10 hours apart.

In addition to radiolabeled platelet recovery and survival measurements, various in vitro assays will be performed on the day of collection at the end of 4°C storage.

One week after the infusion of the radiolabeled aliquot, the subject will return to receive a second radiolabeled aliquot of fresh platelets. To facilitate this, on the morning of the second infusion, the subject will return for collection of a 43 mL blood sample. The blood will be processed to obtain a fresh sample of the subject's platelets to serve as a control comparator. The platelets will be radiolabeled with In-111. The subject will return later in the day for infusion of the radiolabeled fresh 'control' comparator aliquot. Follow-up blood samples will be drawn at ~2 hours after the infusion on Day 0 and then on Days 1, 2, 3, 4 or 5, and 6 or 7 day post infusion to calculate recovery and survival of the subject's fresh vs. stored platelets.

Inclusion Criteria:

• Weight: ≥ 110 pounds
• Platelet count: ≥ 150X10^3/mL
• Hematocrit: 38% for females, 39% for males, but not >55%
• Temperature: ≤ 99.5 F
• Resting blood pressure: systolic ≤180 mmHg; diastolic ≤ 100 mmHg
• Resting heart rate: 40 to 100 beats per minute
• Subjects must be: at least 18 years old, of either sex
• Subjects must be able to read, understand and sign the informed consent document and commit to the study follow-up schedule. The ability to read and speak English is required for participation.
• Subjects must have good veins for apheresis platelet collection and drawing blood samples.
• Subjects of child-bearing potential (either male or female) must agree to use an effective method of contraception during the course of the study. The following methods of contraception are be considered effective; abstinence, intrauterine contraception devices, hormonal methods, barrier methods or history of sterilization.

Exclusion Criteria:

Healthy subjects will be excluded from the study for any of the following reasons:

• Unable to achieve target platelet yield of 3.0 X 1011/unit per Trima Accel (apheresis machine) configuration parameters.
• Ever received radiation therapy.
• Already participated in 4 research studies involving radioisotopes within the contemporaneous calendar-year.
• Taken aspirin, non-steroidal anti-inflammatory, or other platelet affecting drugs within 72 hours of collection or infusion. Subjects who have ever been prescribed anti-platelet medications (e.g. clopidogrel) will be excluded from study participation regardless of the interval to their last dose.
• Currently pregnant or nursing as assessed during interview. A urine pregnancy test prior to radioisotope infusion is required for women of childbearing potential.
• Unable to comply with the protocol in the opinion of the investigator.
• Donated granulocytes within the last 2 days.
• Donated whole blood within the last 7 days.
• Donated platelets or plasma within the last 28 days.