you were just hired as a researcher in an in an immunology lab. Your first task in the lab is to inject mice with a sufficient dose of live pneumococcus bacteria so it dies from the infection within a few days. You also heat-up (but not boil) some of the Pneumococcal bacteria to kill the cells and inject the heat-killed bacteria into the mice. These mice do not succumb to the infection and it will survive a subsequent injection of a normally lethal dose of this organism; such a mouse has now been immunized and is therefore specific to Pneumoccus and the immune mice will retain normal susceptibility to other organisms which it had not previously been exposed. Such specificity shows the immunity we see is a result of the mouse’s adaptive response. Describe an experiment showing that the protective response is solely based on humoral immunity.
Adaptive immunity can be of two types: cell-mediated and humoral immunity. Humoral immunity is also referred to as antibody-mediated immunity because it works on the response of antibodies against certain antigens already present in an organism. Now, to prove that the above response is solely because of humoral immunity, we must make sure that the cell-mediated immune response is stricken off to prove the context.
Blood serum contains all proteins (including the antibodies) but does not contain the cellular part of blood. Thus, it can be used to prove humoral immunity.
Once heat-killed bacteria are administered to a mouse, it develops the antibodies against the microorganism. Thus, we can isolate blood serum from such a mouse and administer this serum to a healthy uninfected mouse. After that, this healthy mouse is infected with live pneumococcus to observe the effects of infection. This mouse does not succumb to the infection and survives. This shows that the serum administered from the mouse that was injected with heat-killed pneumococcus helps the new mouse to survive the infection through non-cell-mediated branch of adaptive immunity, which is humoral immunity. The blood serum provides all the necessary antibodies to mount an antibody-mediated immune response.