Lab #2: Spatial and Temporal Scale

Neutrophils

In this experiment, we are trying to monitor the endocytosis of E. coli by neutrophils, which plays a major role in our innate immune system. Neutrophils are obtained from Tristian and Gabe using the following protocol.

Neutrophils preparation

Humidify a plastic dish with two chambers by incubating with a PBS-wetted cloth in the 42 deg. Celcius water bath. Wash the dish with 1x PBS and place a small amount of blood in each chamber. The dish is kept in a 37 deg. Celcius incubator for 30 minutes. After the blood coagulate, remove the scab from it. Wash the dish again with warm 1x PBS for several times until it is clear. Introduce E. coli to each chamber and image the samples under the scope equipped with a camera.

The followings are the pictures of neutrophils and E. coli. Ten seconds interval in between each frame.

A movie of Neutrophils and E. coli can be downloaded here. Neutrophils and E. coli

Density of Red Blood Cell and Neutrophils

No endocytosis of E. coli is observed due to the fact that all the neutrophils are dead. One possibility is due to the slow scab removal and PBS washing step. Neutrophils die immediately under an environment that is very different from the blood. These include rapid change in temperature, pH, and humidity.

From the pictures above, there are approximately 12 red blood cells and 3 neutrophils in each 0.25mm-by-0.3mm frame. Assuming the PBS solution is 1mm in height, the concentration of RBC will be ~1.6*10^5 RBC/mL and the concentration of neutrophils will be ~40000 Neutrophils/mL. For an average adult, the total blood volume is approximately 1/11 of the body weight. So, a person that weighs 68kg will have a blood volume ~5L. If we use the approximations above, this person will have a total of 8*10^8 RBCs and 2*10^8 neutrophils in his blood streams.

Studies have shown that people, who live at high altitudes, will have an extra 1.9 liters of blood than people who live in low altitudes. This increases the number of RBCs carrying in the blood steams and help to deliver additional oxygen to the body cells.