The overall goal of this procedure is to efficiently isolate skin resident T cells from human skin biopsies. This is accomplished by first obtaining human skin biopsies using a round biopsy punch. Next, each skin biopsy is cut into four smaller pieces in a petri dish.
Then, the skin tissue is mechanically and enzymatically dissociated to produce a single cell suspension. Finally, the skin resident lymphocytes are analyzed by flowing cytometry and cultured ex vivo. Ultimately, sufficient numbers of viable human skin resident lymphocytes can be isolated and analyzed by immunostaining and FACS analysis.
This method will help to answer key questions in dermatology and skin tumor immunology. As for example, how resident T cells in the skin contribute to the disease. Demonstrating the procedure will be Xuehui He, a PhD student from our lab.
After preparing culture medium, according to the text protocol, add two milliliters of complete medium to three wells of a sterile six well culture plate. Then, use a four millimeter round biopsy punch to obtain a skin biopsy. Place it in RPMI 1640 complete culture medium and leave them on the bench for up to four hours, or at four degrees Celsius over night.
While the biopsy is incubating, label a blue capped dissociation tube and add five milliliters of complete culture medium. Next, use sterile tools to place the biopsy into the first well to rinse it. Transfer the tissue to the second well, rinse, and then repeat the process one more time in the third well.
Transfer the well rinsed skin biopsy to a sterile petri dish and pipette 100 micro-liters of complete culture medium on top of the sample. Then, use a stainless steal disposable sterile scalpel to carefully scrape off the subcutaneous fat tissue. In a fresh sterile petri dish, cut each skin biopsy into four smaller pieces.
Then transfer the samples to the prepared dissociation tube containing five milliliters of complete medium. Tightly cap the tube and attach upside down to the sleeve of the automated tissue dissociator. Make sure that all sample material is located in the area of the rotor.
Next, start the dissociation process by running program M spleen zero one. To dissociate the biopsy at the appropriate rotating speed for 56 seconds. After processing, detach the dissociation tube from the dissociator and make sure that all the dissociated material is collected at the bottom of the tube.
Add 150 micro-liters of collagenous one A to the dissociation tube and incubate the sample in a shaking water bath at 37 degrees Celsius for 60 minutes. Then, add 100 micro-liters of DNase into the dissociation tube and mix well. Attach the dissociation tube to the sleeve of the automated tissue dissociator and run program M spleen zero one to dissociate the biopsy one more time.
Then, place a 70 micro-molar nylon cell strainer on the top of a 50 milliliter falcon tube and apply the dissociated sample materials to the cell strainer to remove cell clumps and tissue debris. Use five milliliters of complete medium to wash the cell strainer once. Then, centrifuge the filtrate at 450 G and 20 degrees Celsius, plus or minus two degrees for 10 minutes before aspirating the supernatant.
After repeating the wash step one more time, use 300 micro-liters of complete culture medium to re-suspend the cell pallets. Single cell suspensions are now ready for further analysis. To carry out intracellular cytokine staining, use PMA, ionomysin, and brefeldin A to stimulate the cells and incubate at 37 degrees Celsius and five percent carbon dioxide for four hours before performing flow cytometry analysis.
To perform polyclonal activation of skin resident T cells, aliquot 100 micro-liters of single cell suspension into a round bottom 96 well plate. Add anti-CD3, anti-CD28 mass antibody coated microbeads, recombinant human cytokine, IL-2 and IL-1B. With a well labeled weight lid, cover the culture plate and incubate at 37 degrees Celsius, five percent carbon dioxide, and 100%humidity.
Then, when the color of the medium turns yellow, change it. A clear cell colony can be observed on day eight in cell culture. To carry out FACS analysis, transfer cells of interest into a V bottom 96 well plate.
Centrifuge at 450 G and 20 degrees Celsius, plus or minus two degrees for two minutes. Then, aspirate the supernatant. Use 100 micro-liters of prepared fluorescent 780 conjugated fixable viability to dye to stain the cells by incubating at four degrees Celsius for 30 minutes.
Then, add 100 micro-liters of FACS buffer and centrifuge before aspirating the supernatant. Next, after selecting the cell surface marker monoclonal antibodies from the list provided in the text protocol, use FACS buffer to prepare the antibody solutions. Use isotope control of the antibodies together with a non-stained sample to define gate settings.
Now, add 25 micro-liters of prepared mouse antibodies mixture into each well and protect from light. Incubate at 20 degrees Celsius for 20 minutes. Add 100 micro-liters of FACS buffer, centrifuge, and aspirate the supernatant.
Using buffers prepared for foxp3 staining according to the text protocol, add 100 micro-liters of fixation and permeabilization buffer to re-suspend the pallets. Mix well and incubate at four degrees Celsius for 30 minutes. Then, add 100 micro-liters of permeabilization buffer to each well and centrifuge before aspirating the supernatant.
After washing the cells one more time and choosing the correct antibodies, add 20 micro-liters of prepared monoclonal antibody mixture into each well and protect from light before incubating at four degrees Celsius for 30 minutes. Using permeabilization buffer, wash the cells one more time. Then, use 110 micro-liters of FACS buffer to re-suspend the pallets and transfer the cell suspensions into mico FACS tubes.
Finally, if the exact cell number is required, at 10 micro-liters of a well mixed uniform suspension of flurospheres to each sample immediately before taking FACS measurements. As shown here, different types of CD45 positive leukocytes were identified in single cell suspensions derived from skin of healthy individuals. Including CD4 positive T cells, CD8 positive T cells, and CD11c positive dendritic cells.
Whereas few B cells, NK cells, or micro phages were observed. In addition, the methodology allows for the analysis of CD4 positive CD25 positive foxp3 positive cells in human skin biopsies. For example, by using intracellular staining after fixation and permeabilization, it is possible to demonstrate expression of the transcription factor foxp3 in CD25 positive T cells.
As demonstrated here, to avoid background auto fluorescence and to avoid the auto fluorescent cell population, the anti-human CD45 mouse antibody conjugated to a brilliant violent 421 fluorochrome is recommended for gating of the lymphocyte population. This figure illustrates that the majority of resident cells in human skin were CD3 positive T cells. For cell viability analysis, a fixable viability dye is recommended to distinguish viable from dead or dying cells.
For further functional analysis, by using a single four millimeter skin biopsy of lesional skin from psoriasis patients, it was shown that biopsy derived T cells produced IL-17a and inteferon gamma. Following a four hour stimulation with PMA ionomycin in the presence of brefeldin A.Finally, this figure shows that T cells from psyoriatic individuals have a much higher capacity to produce the psoriasis associated cytokines IL-17a and interferon gamma. Don't forget that working with human tissue and laboratory agents can be hazardous.
Always take safety measures into account.
