As we continue to delve further into Platelet Rich Plasma and how it treats conditions, the most common questions that arise during discussions are:
- Do we want white blood cells in our PRP?
- If so, which white blood cells do we want to include?
In this post, we will explore the different types of white blood cells, their functions and whether they are beneficial or detrimental in Platelet Rich Plasma.
What are White Blood Cells?
White Blood Cells (WBCs), also known as Leukocytes, make up the majority of the body’s immune system. Their main purpose is to protect the body from foreign substances and various types of infections.
What are the different types of White Blood Cells?
- Neutrophils
- Monocytes
- Lymphocytes
- Eosinophils
- Basophils
What are their functions and are they beneficial when included in Platelet Rich Plasma?
1. Neutrophils
- Basic Function: Neutrophils are the first responders during an infection or injury. When there is a site of injury, they destroy germ cells through a process called phagocytosis, which in Ancient Greek literally means “to devour”. Neutrophils also kill invading cells through the release of reactive oxygen species and antimicrobial peptides which are toxic to the invading germ cells. 1
- Role in PRP: Neutrophils have been shown to release damaging molecules which can degrade collagen and other tissues along with extracellular matrix molecules. Neutrophils also release pro-inflammatory cytokines which leads to further damage in the tissue. Therefore, their inclusion in Platelet Rich Plasma, specifically for arthritic applications, is not recommended. 2
2. Monocytes
- Basic Function: The three main functions of monocytes are: phagocytosis, facilitation of communication between the innate and adaptive immune systems, and cytokine production.3
- Role in PRP: It has been found that Monocytes are associated with an increase in cellular metabolism and collagen production in fibroblasts. It has also been found that monocytes moderate the release of anti-angiogenic cytokines such as interferon-ɣ and IL-12.4 Therefore their inclusion in Platelet Rich Plasma is considered beneficial.
3. Lymphocytes
- Basic Function: Lymphocytes are the patrolling cells in the circulatory system that are responsible for recognizing and responding to invading pathogens. They are characterized into three subtypes: T-Cells, B-Cells and Natural Killer Cells (NKCs). T and B cell’s main function are to recognize pathogens and moderate the inflammatory response through the release of cytokines and antibodies. They also are accountable for adaptive immunity, meaning should the same pathogen be encountered again, the body is ready to respond with antibodies. Natural Killer Cells play a major role in defending the body from both tumors and virally infected cells. They are activated when cytokines (called interferons) are released, and produce cytotoxic granules that specifically destroy the altered cells.
- Role in PRP: Currently the significance of Lymphocytes in Platelet Rich Plasma unknown. It is known that platelets activate Lymphocytes as part of the healing cascade through elevated levels of IL-6, however their benefit or detriment to PRP is still unclear.
4. Eosinophils
- Basic Function: Eosinophils are most commonly known as a defense mechanism against parasites and are important mediators of allergic reactions.
- Role in PRP: Eosinophils are known to produce several beneficial growth factors including VEGF, PDGF and TGF-β. These growth factors are associated with angiogenesis, cellular proliferation and extracellular matrix formation.5 Therefore their inclusion in Platelet Rich Plasma may be beneficial in tissue repair.
5. Basophils
- Basic Function: Basophils are also recognized to play a role in parasite defense and allergic reactions. They release several proteins that increase vascular permeation and regulation of the inflammatory process.
- Role in PRP: The role of Basophils for PRP are relatively unknown. Basophils are known to secrete pro inflammatory cytokines but little is known if these are beneficial or detrimental to a PRP sample.
What is the bottom line?
With the current knowledge and research surrounding White Blood Cells, it is generally understood that a PRP sample should include an increase in Monocytes and a decrease in Neutrophils. Knowledge regarding the role of Lymphocytes, Eosinophils and Basophils in PRP is still limited, therefore absolute decisions on their inclusion or exclusion cannot be made. But as our understanding of White Blood Cells and their roles in PRP continue to evolve, formulations of PRP in the future may change to treat a specific condition, moving this from a personalized medicine to a precision medicine.
Stay tuned for our next blog where we will answer your questions about Platelet Rich Plasma. To submit a question for our next blog, email heatherw@companiontherapy.com.
References:
- Mayadas, T. N., Cullere, X., & Lowell, C. A. (2014). The Multifaceted Functions of Neutrophils. Annual Review of Pathology, 9, 181–218. http://doi.org/10.1146/annurev-pathol-020712-164023
- Helen L. Wright, Robert J. Moots, Roger C. Bucknall, Steven W. Edwards; Neutrophil function in inflammation and inflammatory diseases. Rheumatology (Oxford) 2010; 49 (9): 1618-1631. doi: 10.1093/rheumatology/keq045
- Nichols, B. A., Bainton, D. F., & Farquhar, M. G. (1971). DIFFERENTIATION OF MONOCYTES : Origin, Nature, and Fate of Their Azurophil Granules. The Journal of Cell Biology, 50(2), 498–515.
- Sundman, E.A. et al. (2013). The Anti-inflammatory and Matrix Restorative Mechanisms of Platelet-Rich Plasma in Osteoarthritis. The American Journal of Sports Medicine.Vol 42, Issue 1, pp. 35 – 41
- Duarte, J. et al. Platelet-Rich Plasma: Regenerative Medicine: Sports Medicine, Orthopedic, and Recovery of Musculoskeletal Injuries. Springer Science & Business Media, Oct 29, 2013 pp 220