PBMCs – The one stop immune cell shop

PBMCs are a mixed population of single nucleus myeloid and lymphoid cells. PBMCs can be further purified to isolate individual cell types such as natural killer cells, T cells, and B cells. In addition, PBMCs are a rich source of monocytes, which can be directed to differentiate into either macrophages or dendritic cells through culture with various cytokines.

The figure illustrates the cellular composition of whole blood as well as the various myeloid and lymphoid cells.

The lymphoid cells include lymphocytes such as B cells, T cells, and Natural Killer (NK) cells. 

• B cells are involved in the humoral, or antibody-mediated adaptive immune response, and are defined by the B-cell receptor (BCR) on their cell surface and the production of antibodies. 
• Conversely, T cells are involved in the cell-mediated adaptive immune response and are defined by the T-cell receptor (TCR) on their cell surface. 
• NK cells also play a cytotoxic role. However unlike T cells, NK cells do not require MHC presentation in order to recognize and destroy. Thus, they can be considered immune system first responders. 

The myeloid cells include monocytes, dendritic cells, and macrophages. Monocytes circulate through the blood to different tissues, where they differentiate into tissue-resident macrophages and dendritic cells.

• Macrophages engulf and destroy foreign substances and cancerous cells. Resident macrophages maintain a steady state of general tissue repair, while some macrophages that are created through a specific immune response are trained to target and destroy specific foreign cells. 
• Similar to macrophages, dendritic cells also engulf and destroy foreign cells in their immature state. As dendritic cells mature, they turn from destruction to processing and presentation of foreign antigens to T cells. Thus, dendritic cells are also aptly called antigen-presenting cells (APCs).

Isolating PBMCs is a common primary step in purifying individual immune cell types. Plasma, PBMCs, and RBCs all have different densities, making them relatively easy to separate using a density gradient reagent.

Briefly, whole blood is diluted, layered over the density gradient reagent, and then centrifuged. During centrifugation, the cells separate based on their density, leaving behind visible layers with distinct cell populations (see image below). The mononuclear layer from which PBMCs are collected is often times called the “buffy coat”.

Depending upon research needs, you are then able to collect the different cell populations and either use directly or isolate specific cell types contained in the PBMC mixture. Individual cell types can be isolated from PBMCs either through immunomagnetic separation or FACS (fluorescence-activated cell sorting) techniques.

After isolation, it is best to characterize the cells you have isolated to be sure they are a pure population of the correct cell type.

Another starting source material can be from leukopaks. A leukopak is a highly-enriched leukapheresis-derived product obtained from an IRB-approved collection facility. Leukopaks contain higher concentrations of mononuclear cells, B cells, T cells, stem/progenitor cells, dendritic cells, and other cell types as compared to standard venipuncture collection methods or buffy coat products. Lonza provides options in the types of leukopaks it offers from fresh leukopaks, cryopreserved leukopaks to mobilized leukopaks.

Lonza is committed to providing you with multiple options for your immune cell needs. We provide a readily available, consistent source of purified and characterized peripheral blood cells, including PBMCs, CD14+ monocytes, dendritic cells, CD4+ T cells, and natural killer (NK) cells and leukopaks. 

Alternatively, you can skip the hassle of isolation and characterization by purchasing commercially purified and characterized cells. 

Whether you are isolating a specific cell type or modeling complex immune responses to drugs or diseases, Lonza cryopreserved PBMCs offer the quality, purity and function needed to help achieve research goals. We maintain inventory from a diverse donor population, allowing you to choose lots based on donor demographic characteristics to develop a representative sample group that works for you.