Human Immunity and Blood

Kupffer cells are the resident macrophages of the liver that phagocytose old blood cells and pathogens.

In many lower vertebrates, the liver serves as a hematopoietic organ, producing various blood cells including lymphocytes, unlike in mammals where this is primarily the role of bone marrow.

Fibrin is a tough protein substance that is arranged in long fibrous chains; it is formed from fibrinogen, a soluble protein that is produced by the liver and found in blood plasma. In the clotting mechanism, fibrin threads form a meshwork for the basis of a blood clot. Most of the fibrinogen in the circulating blood is formed in the liver.

When antibodies bind to a microbe, they often act as a marker that makes it easier for phagocytes (a type of white blood cell) to identify and engulf the pathogen through a process called phagocytosis.

Non-specific immune responses are the body's first line of defense, such as skin, mucus, and tears, which act as physical or chemical barriers. Antibodies and memory cells are part of the specific (adaptive) immune response.

O-negative (O-) blood is known as the universal donor type because its red blood cells lack A, B, and Rh antigens, meaning it can be transfused to patients of any blood type without triggering an immune reaction.

Breast milk is a complex biological fluid containing macronutrients like protein, immune cells like white blood cells, and protective antibodies (such as IgA) that help build the baby's immune system. Therefore, all of the listed components are passed to the baby.

Type O blood is considered the universal donor because its red blood cells do not have A or B antigens on their surface, meaning it can be transfused into patients of any blood type without causing an immune reaction.

Individuals with blood type O (specifically O negative) are considered universal donors because their red blood cells do not have A, B, or Rh antigens on their surface, preventing an immune response in recipients of any blood type.

Individuals with blood type AB (specifically AB positive) are universal recipients because their blood contains both A and B antigens and lacks anti-A and anti-B antibodies, meaning they can receive red blood cells of any type.

A person with type A blood has anti-B antibodies in their plasma, meaning they cannot receive blood containing B antigens (types B and AB). Therefore, they can only safely receive type A or type O (the universal donor) blood.

Registration involves administrative tasks like showing ID, filling out demographic forms, and reading educational materials. Measuring temperature, blood pressure, and hemoglobin is part of the health history/physical screening phase that occurs after registration.

Red blood cells, or erythrocytes, have an average lifespan of about 120 days in the human body. After this period, they become worn out and are destroyed by macrophages in the spleen and liver. New red blood cells are continuously produced in the bone marrow to replace them.

The cellular portion of human blood consists of three primary types of cells: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Each type has a distinct and vital role, such as oxygen transport, immune defense, and blood clotting. Together, they make up about 45 percent of blood volume.

Platelets (thrombocytes) are cell fragments in the blood that play a crucial role in blood clotting to stop bleeding when blood vessels are damaged. Red blood cells (RBCs) transport oxygen, and white blood cells (WBCs) are involved in the immune response.