Human Immunity and Blood

The '+' or '-' in blood types refers to the presence (+) or absence (-) of the Rh factor, a protein on red blood cells. Type A positive means the person has A antigens and the Rh factor protein on their red blood cells.

Rh factor stands for Rhesus factor, named after the Rhesus monkey in which it was first discovered. It refers to a protein antigen on red blood cells that is important in blood typing and pregnancy complications.

AB negative is the rarest blood type globally, but among the broad ABO groups, AB is the least common. O+ is actually the most common, making it a distractor. AB individuals have both A and B antigens, which occurs less frequently in the population than other combinations.

Mature mammalian red blood cells (RBCs) lack a nucleus to create maximum space for hemoglobin, the oxygen-carrying protein. This enucleation happens during RBC development in the bone marrow. Option B is incorrect because mammalian RBCs lose their nucleus before entering circulation. Other vertebrates (birds, fish) do have nucleated RBCs, but the question clearly refers to human biology.

Red blood cells are scientifically called erythrocytes. Platelets are thrombocytes, leukocytes are white blood cells, and hemoglobin is the oxygen-carrying protein within red blood cells.

Hematology is the branch of medicine concerned with the study of blood, blood-forming organs, and blood diseases. The term comes from Greek 'haima' (blood) and 'logia' (study). Nerves, lungs, and tendons are studied by neurology, pulmonology, and orthopedics respectively.

Erythrocytes (red blood cells) contain hemoglobin, the iron-rich protein that binds oxygen and transports it throughout the body. Leukocytes are white blood cells and platelets are cell fragments involved in clotting.

Blood cancer primarily affects white blood cells which are produced in the bone marrow. Leukemia involves the overproduction of abnormal white blood cells that crowd out healthy blood cells. Lymphoma and myeloma are other types of blood cancer that specifically affect lymphocytes and plasma cells respectively.

Type O blood lacks A and B antigens on red blood cells, making it compatible with all other blood types in transfusions. This is why Type O individuals are called universal donors. Type A can only donate to A and AB, Type B only to B and AB, and Type AB can only donate to AB.

White blood cells (leukocytes) are the primary cells of the immune system that protect the body from infection and disease. Red blood cells carry oxygen, nerve cells transmit signals, and platelets help with blood clotting (option D is misspelled).

Type AB blood has both A and B antigens on red blood cells and no antibodies against either type in the plasma. This allows people with AB blood to receive red blood cells from any blood type (A, B, AB, or O) without having an immune reaction. Types A, B, and O all have antibodies that would attack some donor blood types.

White blood cells (leukocytes) are the immune system's primary defense cells. They identify and neutralize pathogens like bacteria, viruses, and foreign substances. White blood cells include lymphocytes (T cells and B cells), macrophages, and neutrophils, each playing different roles in protecting the body from infections and diseases. Red blood cells carry oxygen, platelets help with clotting, and nerve cells transmit signals.

Type O blood lacks A and B antigens on red blood cells, making it compatible with all other blood types. This universal donor property is crucial in emergency transfusions when the recipient's blood type is unknown.

Blood groups A, B, AB, and O are classified based on antigens present on red blood cells. Type A has A antigens, Type B has B antigens, Type AB has both, and Type O has neither. Antibodies in plasma determine compatibility, but antigens on RBCs define the type.

Platelets (thrombocytes) are cell fragments responsible for blood clotting. They form plugs at injury sites and release clotting factors. Red blood cells transport oxygen, white blood cells fight infection, and lymph nodes are immune system organs - none of these handle clotting.