An In Vivo Mouse Model to Measure Naïve CD4 T Cell Activation, Proliferation and Th1 Differentiation Induced by Bone Marrow-derived Dendritic Cells

This method can help answer key questions in the immunology field about T-cell activation, proliferation, and Th1 differentiation, as well antigen presenting cell stimulation of adaptive immunity. The main advantage of this technique is that it allows the study of an in vivo environment while simultaneously allowing cell manipulation in vitro. Visual demonstration of this method is critical as the organ and bone isolation and adoptive transfer steps are difficult to master through text instructions alone.

For bone marrow cell isolation, disinfect the hind limbs of an adult mouse with 70%ethanol and use scissors to make a lateral skin incision across the hind limbs. Insert scissors at the medial aspect of the legs, and cut the skin with the scissors until the beginning of the hind limbs. Then use forceps to separate the skin from the legs.

Using scissors, separate the muscle from the femur and tibia, and use scissors to disarticulate the hip joint, breaking the femur head. Then separate the femure from the tibia without breaking the bone ends, and place the bones in a petri dish of complete medium on ice. When all of the bones have been harvested, carefully cut off the proximal and distal ends of each bone with a scalpel, and use a 1 millileter syringe equipped with a 25-guage needle to flush the bones repeatedly with a total volume of 10 millileters of warm complete RPMI medium.

When all of the bones have been flushed, transfer the entire contents of the dish to a 50-millileter conical tube fitted with a 70-micrometer pore nylon web filter, and carefully dislodge any debris and cell conglomerates with gentle stirring and pipetting. Collect the bone marrow cells by centrifugation. Resuspend the pellet in one millileter of four-degree Celsius red blood cell lysis buffer with pipetting, and incubate the mix on ice for five minutes.

At the end of the incubation, stop the lysis with 10 millileter of PVS, and resuspend the pellet in 25 millileters of complete medium for a second centrifugation. Then resuspend the cells in 5 millileters of fresh complete medium for counting, and centrifuge the cells again. For secondary lymphoid tissue cell isolation, collect the inguinal, axillary, brachial, cervical, and mesentaric lymph nodes, and spleen from OT-II transgenic mice, and transfer the secondary lymphoid tissues into a plastic petri dish containing 10 millileters of complete RPMI medium.

When all of the tissues have been harvested, transfer the lymph nodes and spleen to a 70-micrometer cell strainer in a 50-millileter conical tube, and use a syringe plunger to homogenize the tissues. Flush the strainer with up to 15 millileters of medium, and spin down the cells by centrifugation. Then isolate the CD4-positive T cells by magnetic bead sorting, according to standard protocols.

For in vivo activation of the naive OT-II CD4-positive T-cells, label the magnetic bead-isolated T-cells with vital cell tracer dye, according to standard protocols, and resuspend the labeled cells at a 10 to the sixth cells per 100 microliters of PBS concentration. Then adoptively transfer 100 microliters of cells per animal via the tail vein. Pre-warm the mice before the injection in order to ensure that the tail veins are enough dilated to allow delivery of entire cell volume.

After 24 hours, deliver 10 to the fifth LPS-matured OVA peptide-loaded dendritic cells by subcutaneous injection into the foot pad of each T-cell injected animal. Two and five days after the adoptive challenge, harvest the poplitial lymph nodes from the recipient animals for tissue processing and T-cell isolation, as demonstrated. To analyze T-cell activation, stain day two-isolated cells with fluorescent antibodies against CD4, CD69, and CD25 to determine the percentage of CD64-positive, CD25-positive T-cells within the recipient CD4-positive population by flow cytometry.

To assess T-cell proliferation, stain day five-isolated cells with the appropriate fluorescent antibodies against CD4, and analyze the decay of the vital cell tracer dye signal in the donor CD4-positive T-cell population by flow cytometry. To evaluate Th1 differentiation, plate four times 10 to the fifth day five-isolated T-cells per well in 200 microliters of complete medium, supplemented with ionomycin and PMA per well, in a 96-well plate. Then place the plate in a 37 degree Celsius cell culture incubator for six hours, adding Brefeldin A to each well to block cytokine secretion during the last four hours of the stimulation.

At the end of the incubation, centrifuge the plate, and discard the supernatant by rapid inversion. Stain the cells with anti-CD4 antibody, followed by fixation in 100 microliters of 2%paraformaldehyde and 1%sucrose for 20 minutes at room temperature. Permeabilize the cells with 50 microliters of permeabilization buffer for 30 minutes at 4 degrees Celsius, followed by a centrifugation wash with 150 microliters of PBS per well.

Next, stain for the intracellular cytokines of interest, according to standard protocols for 30 minutes at room temperature, followed by two centrifugation washes with 150 microliters of PBS supplemented with 1%saponin per well. Then, analyze the cells by flow cytometry. Flow cytometric analysis of GM-CSF bone marrow-derived dendritic cells after LPS stimulation, reveals an upregulation of maturation markers, such as MHCII, CD80, and CD86.

Naive CD4 positive OT-II T-cells become activated after adoptive transfer to recipient animals by their upregulation of T-cell activation markers surface expression, and multiple rounds of cell division. Upon activation, the proliferating CD-positive OT-II T-cells demonstrate a Th1 phenotype, as demonstrated by their intracellular interferon gamma expression. Once mastered, this technique can be completed in eight hours if it's performed properly.

While attempting this procedure, it's important to remember to prepare all the reagents and materials the day before the experiment. After its development, this technique paved the way for researchers in immunology to study dendritic cells and T-cells in mice. After watching this video, you should have a good understanding of how to isolate bone marrow from the femurs and tibia of mice, and how to transfer T-cells and dendritic cells to recipient animals.

Don't forget that working with sharp instruments such needles, scalpels, or scissors, can be extremely hazardous, so precautions such as using the appropriate finger protection should always be taken while performing these procedures.