NK Cells Should Be Stored for No More Than 24 Hours

Introduction

It is best to store NK cells and NKT cells for no more than 24 hours at 4 °C, and the best preservation effect is physiological saline + 5% human albumin + 1% low molecular weight dextran.

With the rapid development of immune cell biology, immunotherapy has become one of the important means of tumor treatment.

Cellular immunotherapy, also known as adoptive immunotherapy, collects the body's own immune cells, cultivates them in vitro, increases their number thousands of times, enhances their targeted killing function, and then infuses them back into the human body to kill blood and tissues. It can break down the pathogens, cancer cells and mutated cells in the body, break immune tolerance, activate and enhance the body's immune ability.

The immune cells used in cellular immunotherapy mainly include natural killer cells (NK cells), natural killer T cells (NKT cells), etc.

After the cells are collected, they need to be resuspended in preservation solution and then transported from the laboratory to the clinic. Because autologous immune cell therapy is an individualized treatment, cell products are different from ordinary biological products and drugs. How to maintain the maximum activity of immune cells and their original biological properties during transportation to ensure that the cells ultimately used in treatment achieve uniformity? Quality standards have become key for immunotherapy.

Immunotherapy has become the most valuable and potential treatment method for tumor treatment.

From 2011, when Professor Ralph M. Steinman of Rockefeller University in the United States won the Nobel Prize in Physiology or Medicine for "the discovery of dendritic cells and their role in adaptive immunity" to 2013, Science magazine listed tumor immunotherapy as a major science of the year. Breakthroughs, and then the discovery that immune checkpoint inhibitors with PD1 as the core drug are more effective, have set off an upsurge in the development of immunotherapy around the world, and immunotherapy has become the most valuable and potential treatment method for tumor treatment.

NK cells are important natural immune cells in the body, accounting for approximately 10% to 20% of peripheral blood lymphocytes. It is not only involved in immune regulation, but also closely related to anti-tumor.

In recent years, more and more studies have proven that NK cells have joined the anti-cancer ranks. NKT cells are a special subset of T lymphocytes that perform important immune regulatory functions in the body and regulate the function of the immune system by secreting cytokines. Therefore, obtaining NK and NKT cells with high proliferative activity in vitro and then infusing them back into the body with a low immune system can enhance the immune surveillance and clearance functions in the body, improve the body's anti-aging ability, and reduce the risk of disease.

No matter which immune cells are used clinically to treat diseases, they must follow the "Technical Guiding Principles for Research and Evaluation of Cell Therapy Products (Trial)" to provide safe and effective cell products for clinical immune cell therapy.

With the rapid development of tumor immune cell therapy, cells will be stored and transported in a short period of time more and more frequently. How to ensure that the biological properties of cells in storage bags do not change to the greatest extent in the short term is the exploration goal of many laboratory personnel. This includes the composition of the preservation solution, preservation time and temperature, etc. A large number of experiments have proven that whether immune cells or stem cells, cells are in the best condition at a constant temperature of 4°C.

Effects of different cell preservation solutions on short-term storage of NK cells and NKT cells

A scientific research team composed of the Experimental Management Center of Southern Medical University, the School of Medicine of Foshan University of Science and Technology and other institutions published a paper titled "The short-term preservation of natural killer cells and natural killer T cells by different cell preservation solutions" in the Journal of Shenyang Medical College, a professional industry journal . "Influence " research results.

The report pointed out that in order to explore the changes in the biological properties of natural killer cells and natural killer T cells after being stored in different preservation solutions for 0, 6, 12, and 24 hours under 4C transportation and storage conditions, it provides a reliable basis for the preservation and transportation of immune cells. experimental basis.

The researchers collected four 40ml blood samples and divided the cells from the same peripheral blood into two parts according to the NK cell and NKT cell culture protocols. Collect 8 cultured NK cells and NKT cells respectively and apply physiological saline (preservation solution A), normal saline + 5% human albumin (preservation solution B), normal saline + 5% human albumin + 1 % low molecular weight dextran (preservation solution C) and three preservation solutions. Cell viability and clumping rate, flow cytometry and cell killing experiments were measured at 0, 6, 12 and 24 hours respectively.

Results: When stored for 12 hours, the cell viability rate of group A was lower than 85%, and the difference was statistically significant compared with the other two groups (P<0.05); when stored for 24 hours, the cell viability rate of each group was lower than 85%, but The cell viability rate in the preservation solution of group A was significantly lower than that of groups B and C (P<0.05). When stored for 12 and 24 hours, the cell clumping rate in the preservation solution of groups B and C was lower than that of group A, and when stored for 24 hours, the clumping rate of group C was lower than that of group B (P<0.05). Until 24h, there were no significant changes in the flow cytometry results in each treatment group. Compared with the cells in group C, the killing effect of NK cells and NKT cells in group A was significantly weakened when stored for 12 hours (P<0.05). With the extension of storage time, the killing power of cells in each group decreased significantly by 24 hours. Group A, The lethality of cells in group B was significantly different from that in group C (P<0.05).Conclusion: It is best to store NK cells and NKT cells for no more than 24 hours at 4°C, and the preservation effect is best with normal saline + 5% human albumin + 1% low molecular weight dextran.

In short, this study explored the effects of short-term storage of NK cells and NKT cells in different preservation solutions on the viability, clumping rate and lethality of NK cells at 4°C and found that NK cells and NKT cells were stored in normal saline + 5% Storage in HSA+1% low molecular weight dextran storage solution provides the best effect, but it should not exceed 24 hours. This study explores the scientific nature and standardization of immune cell preservation and provides scientific research basis.