Understanding the Immune System and Infectious Diseases

The immune system is vital for health, protecting against harmful germs like bacteria and viruses.
It is composed of cells, tissues, and organs working in coordination.
This system distinguishes between the body's own cells and foreign invaders, attacking only the harmful ones.
General defenses, such as skin barriers, and specific responses, involving T cells and B cells, are utilized.
T and B cells destroy germs and remember them for a faster response upon re-exposure
Overall, the immune system maintains health and combats illnesses.

Pathogens are microorganisms that can cause sickness.
Bacteria are single-celled organisms that can rapidly multiply and lead to conditions such as strep throat or food poisoning.
Viruses require a living cell for growth an example of this is the flu or COVID-19.
Fungi, including molds and yeasts, cause infections, for example, athlete's foot.
Parasites reside on or inside other organisms, leading to diseases such as malaria.
An infectious disease arises when pathogens invade the body, resulting in illness and discomfort.

Antigens are unique markers on cell surfaces that enable the immune system to distinguish between the body's own cells and foreign entities.
The body's own cells possess self-identifying antigens.
Foreign pathogens, like bacteria or viruses, display non-self antigens that trigger an immune response.
The immune system initiates an attack against pathogens.
Telling the difference between self and non-self is key for staying healthy and preventing infections.

Innate immunity is the body's preliminary defense mechanism against infections.
It's rapid in response and targets a broad spectrum of harmful invaders, for instance, bacteria, viruses, and fungi.
It delivers broad protection rather than targeting specific pathogens so is considered non-specific.
The skin serves as a physical barrier to prevent microorganisms from entering the body. The skin produces antimicrobial oils and sweat.
Tears contain enzymes that eliminate bacteria.
Saliva contains enzymes that disrupt bacterial cell walls.
Stomach acid is a potent defense against pathogens.
Phagocytes (macrophages) are specialized white blood cells which engulf harmful microorganisms.
Inflammation is a non-specific immune response to tissue injury or infection, increasing blood flow and immune cell recruitment to affected areas, promoting healing.
A fever is a bodily response to infection, raising body temperature to hinder pathogens and enhance immune cell effectiveness.

Adaptive immunity targets specific pathogens, unlike the rapid and general response of non-specific immunity.
Adaptive immunity develops over time.
It recognizes and attacks specific invaders.
Lymphocytes, including T cells and B cells, are key.
These cells recognize a pathogen's unique antigens and prepare a precise response.
Macrophages engulf and digest pathogens, displaying antigens on their surface.
Macrophages present these antigens to helper T cells, activating and multiplying them.
Activated helper T cells release cytokines, activating B cells to grow and divide.
Some B cells produce antibodies specific to the pathogen.
Activated helper T cells stimulate killer T cells (cytotoxic T cells).
Killer T cells recognize and destroy infected or abnormal cells by recognizing the pathogen's antigens on the surface of body cells.
B cells release antibodies that bind to pathogens, marking them for destruction.
Killer T cells actively seek out and destroy infected cells.
After the infection is cleared, some B cells become memory cells.
Memory B cells enable a quicker, stronger response upon re-exposure to the same pathogen.
The body can effectively fight off infections and attain lasting immunity through this coordinated response.

Antibiotics, antivirals, antifungals, antiparasitics, and vaccines are important tools in medicine used to prevent and treat infections caused by different types of pathogens.
Antibiotics combat bacterial infections by either eliminating bacteria or halting their proliferation, effective against ailments like strep throat and bacterial pneumonia, however, they are ineffective against viruses.
Antivirals are designed to manage viral infections by impeding viral replication in the body, helping manage symptoms and mitigate the severity of the illness, but do not cure viral infections.
Antifungals combat fungal infections by eliminating or inhibiting the growth of fungal cells, commonly employed for conditions such as athlete's foot and yeast infections.
Antiparasitics target parasitic infections caused by worms or protozoa, aiding in eliminating parasites from the body and addressing ailments such as malaria and giardiasis.
Vaccines are measures that enable the immune system to identify and combat specific pathogens with some preventing bacterial infections, while others prevent viral infections.
Vaccines introduce a harmless component of the pathogen into the body, stimulating the immune system to mount a defense of antibodies, thus preventing ailments, for example, measles, polio, and smallpox.
Preventative measures play a crucial role in upholding health and regulating infectious ailments.