The ongoing SARS-CoV-2 pandemic has put immunology research firmly into the global spotlight, generating tremendous interest in this field. The immune system is the body’s defense against microorganisms and disease-causing cellular changes (such as cancer). We are constantly exposed to a variety of microorganisms present in the environment, such as viruses, bacteria and fungi. Harmful microorganisms are pathogenic, beneficial microorganisms are commensal.
The immune system is complex, with many different parts and components. Scientists at St. Jude are studying these aspects of immunity to gain a better understanding of human health and how we respond to disease.
The immune system is composed of organs, cells (commonly called “white blood cells”) and proteins.
The immune system and its response can be broadly grouped into two categories - innate immunity and adaptive immunity.
The purpose of a vaccine is to initiate the priming step required to establish immune memory, a kind of training exercise for the immune system. Vaccinations are small pieces or weakened, non-harmful versions of a virus, bacteria or infectious agent that are given in small amounts to your body, which alert and train your immune system to protect you against future infections with the same agent.
Vaccines teach our immune systems to memorize harmful agents and respond to them quickly if seen again. In this way, vaccines act like an immunologic wanted poster informing your T and B cells who the bad guys are.
The goal of vaccines may be different based on the disease type, but in general, nearly all vaccines are designed to prevent disease severity. Some vaccines are also formulated to reduce disease transmission or reduce the total number of days sick.
One very important aspect to remember about vaccines is that they are not a physical shield preventing you from being exposed to a bacteria or virus, but rather, work with your immune system to reduce or eliminate harm after exposure. Additionally, if you experience symptoms after receiving a vaccine, this is completely normal and a good sign that your immune system has recognized and is responding to the vaccine.
Vaccines have helped substantially reduce and/or effectively eradicate numerous illnesses. For example, in the 20th century (1900-2000) the annual morbidity for measles was 530, 217 whereas in 2021 the annual morbidity for measles was 9, that’s a 99% decrease due to vaccination.
In pandemics, vaccines can help manage the health care burden by reducing illness severity. Pandemic causing microorganisms include Ebola virus, influenza virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and more. Ongoing research also aims to develop vaccines against mutated versions of viruses that haven’t yet occurred.
Multiple vaccines are generally needed for three reasons:
T cells are a type of white blood cell derived from the bone marrow and are members of the adaptive arm of the immune system. T cells help clear active infections, fight cancer and can be trained by a vaccination or infection to protect us against future attacks.
Similar to how a lock recognizes a key, T cells help our bodies fight infections by recognizing small fragments of a pathogen with a complex of proteins that are collectively called a T cell receptor (TCR). This receptor is what gives a T cell its specificity, which leads to its activation and function.
There are also different types of T cells, which protect us in unique ways. T ‘Helper’ cells use their TCRs to train other immune cells, such as aiding B cells to produce antibodies. During an ongoing infection, a second type of T cell, called ‘Killer’ T cells, use their TCRs to recognize infected cells and eliminate them along with any pathogens inside. These Killer T cells also detect and attack cancerous tumor cells.
T cells elicit their protective effects by acting on other cells (Figure, panel B), which is why their responses are referred to as cell mediated immunity. In contrast, B cells produce antibodies which circulate in the bloodstream, and act on the pathogen itself. Protection conferred by antibodies is referred to as humoral immunity. Antibodies generally function by:
Absolutely! Vaccine efficacy varies depending on the pathogen it targets. Part of the challenge in achieving a highly and broadly effective influenza vaccine is its propensity to mutate (as described above). New, or next generation vaccines, seek to improve multiple aspects of vaccine design to achieve optimum vaccine efficacy. For instance, a neat aspect about T cell function, as it pertains to infectious diseases, is that they target proteins that are less prone to mutation, meaning they target the most important pathogen proteins that are unlikely to change and avoid future immune responses. Modifying vaccination strategies to optimize T cell responses is a promising approach to designing broadly effective vaccines that can recognize viruses even when they mutate. Scientists can also apply vaccination concepts from infectious diseases to other illnesses, such as cancer.
Scientists at St. Jude investigate fundamental concepts of T cell biology to develop new therapeutic options and improve existing treatments. Examples of such treatments include custom designing T cells with receptors that recognize and kill cancer cells, also known as chimeric antigen receptor (CAR) T cells. Join us and learn more in upcoming articles that will expand on T cell development and delve into the exciting, groundbreaking research being conducted at St. Jude!
All images created with Biorender.