Human Immunity and Blood

Nearly all gamma delta T-cells in the skin express V gamma 5.

Blood group O (specifically O negative) is called the universal donor because it lacks A and B antigens on red blood cells, allowing it to be transfused to recipients of any blood group in emergencies. AB positive is the universal recipient, while A and B can only donate to their own types and AB.

Langerhans Cell Histiocytosis (LCH) is characterized by proliferation of Langerhans cells which express CD1a as a specific surface marker. CD1a is considered the most specific immunohistochemical marker for LCH. CD57 is found on NK cells, CD3 on T-cells, and CD68 on macrophages/monocytes.

Langerhans Cell Histiocytosis (LCH) is characterized by proliferation of Langerhans cells, which are dendritic cells that normally reside in skin and lymph nodes. These cells pathologically express CD1a, which is a specific immunohistochemical marker for LCH diagnosis. CD57 is typically associated with NK cells, CD3 with T-cells, and CD68 with macrophages.

Cryoprecipitate is a blood product containing Factor VIII, von Willebrand factor, fibrinogen, and Factor XIII. It is prepared by thawing fresh frozen plasma and collecting the precipitate. Factor IX is NOT present in cryoprecipitate - it's found in fresh frozen plasma and prothrombin complex concentrates, which is why hemophilia B cannot be treated with cryoprecipitate.

In chronic hepatitis B, HBsAg and HBeAg are present, but anti-HBs is absent. IgM anti-HBc indicates acute infection; in chronic infection, only IgG anti-HBc is present, while IgM is typically negative.

Cellular marrow means the bone marrow is hypercellular, ruling out aplastic causes. PNH causes pancytopenia due to intravascular hemolysis with cellular marrow. Megaloblastic anemia shows ineffective erythropoiesis with cellular marrow. Myelodysplastic syndrome presents with pancytopenia and hypercellular marrow. Congenital dyserythropoietic anemia primarily affects erythropoiesis with macrocytic anemia but does not typically cause pancytopenia - it is the exception.

Diphtheria is a bacterial infection that primarily affects the throat and respiratory tract. The bacteria Corynebacterium diphtheriae produces toxins that damage throat tissues, creating a characteristic membrane. Blood, liver, and brain are not the primary sites of diphtheria infection.

Blood cancer (leukemia) involves uncontrolled proliferation of white blood cells (WBCs) in bone marrow. This crowds out healthy blood cells. RBCs carry oxygen, platelets help clotting, and hemoglobin is the oxygen-carrying protein in RBCs - none are the primary cancer source.

Anaphylaxis is a severe, potentially life-threatening IgE-mediated allergic reaction. IgE antibodies bind to mast cells and basophils, triggering release of histamine and other mediators that cause widespread vasodilation, bronchoconstriction, and can lead to circulatory shock and asphyxia. Orthopnea is breathing difficulty when lying flat.

Heparin is an anticoagulant substance produced primarily by mast cells, which are connective tissue cells containing granules with heparin and histamine. Mast cells release heparin as part of the inflammatory response and to prevent blood clotting. Other options are incorrect: fibroblasts produce collagen, plasmocytes are antibody-producing plasma cells, and adipocytes store fat.

Blood type O individuals have both anti-A and anti-B antibodies in their plasma because they lack A and B antigens on their red blood cells. Type AB has neither antibody, type A has anti-B, and type B has anti-A.

T8 cells refer to T lymphocytes that express the CD8 co-receptor, which are known as cytotoxic T cells. These cells are responsible for killing virus-infected cells, tumor cells, and damaged cells. T4 cells (CD4+) are helper T cells.

All three diseases are related to the lymphatic system. Hodgkin's disease is a cancer of the lymphatic system (lymphoma). Multiple myeloma is a cancer of plasma cells (which are derived from B lymphocytes in the lymphatic system). Chronic lymphocytic leukemia is a cancer of B lymphocytes.

Hodgkin's disease (Hodgkin lymphoma) is a cancer of the lymphatic system that specifically affects lymphocytes, which are a type of white blood cell. It does not primarily involve erythrocytes (red blood cells) or all leucocytes.