The responses observed in type IV hypersensitivities result from the action of T cells and phagocytes.
Hypersensitivity IV type, also called delayed-type hypersensitivity (DTH), involves T cell-antigen interactions that cause activation and secretion of cytokines. This type of hypersensitivity requires sensitized lymphocytes that respond 24–48 hours after exposure to soluble antigens. A type IV hypersensitivity reaction is a cell-mediated reaction that can occur in response to contact with certain allergens, resulting in what is called contact dermatitis, or in response to certain diagnostic procedures such as the tuberculin skin test. Certain allergens need to be avoided to treat this condition. Type IV hypersensitivity response is observed results from the action of T cells and macrophages while other types are mediated by antibodies. This reaction occurs at least 1–3 days after the initial exposure. Type IV hypersensitivity is the mechanism of many autoimmune disorders.
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The nutrients get to the cells in a flatworms solid acoelomate body by diffusion process. Flatworms feed primarily on protozoa and bacteria, smaller worms and tiny organisms, dead or alive, that they come across. Based on the species of the flatworms , they also consume plant materials. They rely on diffusion to transport oxygen and nutrients to their internal tissues.
7. Adenine (A), Guanine, Cytosine and Thymine are the four nitrogenous bases in DNA.
8. In DNA Cytosine always forms hydrogen bonds with guanine.
9. The sequence of nucleotides carries the genetic information of an organism.
10. The process of replication produces a new copy of an organism's genetic information which is passed on to a new cell.
11. The double-coiled shape of DNA is called a double helix
Explanation:
There are four nitrogenous bases in the DNA of an organism. Two of the bases are pyrimidines eg: Thymine and cytosine while 2 of the bases are purine bases namely adenine and guanine. The purine of one strand forms a hydrogen bond with pyrimidine of the parallel strand of DNA.
The bases are present in nucleoplasm as dNMPs and in DNA they are present as dNTPs (deoxyribonucleotide triphosphate). During replication, these dNMPS keeps on bonding with other dNMPs in the presence of ATP and as DNA Polymerase, ligase topoisomerase etc. These nucleotides form the DNA strands and they are responsible for coding proteins. The sequence of DNA is also termed as gene.
The double helix structure of DNA was given by Watson and Crick. Each strand has an alternative backbone of sugar and phosphate group. The four bases bonds with glycosidic and phosphodiester bonds with sugar and phosphoric acid.
