Given the question: Information:  - Dendritic cells ( DCs ) are antigen - presenting cells ( also known as accessory cells ) of the mammalian immune system . Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system . They act as messengers between the innate and the adaptive immune systems . Dendritic cells are present in those tissues that are in contact with the external environment , such as the skin ( where there is a specialized dendritic cell type called the Langerhans cell ) and the inner lining of the nose , lungs , stomach and intestines . They can also be found in an immature state in the blood . Once activated , they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response . At certain development stages they grow branched projections , the dendrites that give the cell its name (  or déndron being Greek for `` tree '' ) . While similar in appearance , these are structures distinct from the dendrites of neurons . Immature dendritic cells are also called veiled cells , as they possess large cytoplasmic ' veils ' rather than dendrites .  - An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by either chemical or physical means, via ionization.  - The innate immune system, also known as the non-specific immune system or in-born immunity system, is an important subsystem of the overall immune system that comprises the cells and mechanisms that defend the host from infection by other organisms. The cells of the innate system recognize and respond to pathogens in a generic way, but, unlike the adaptive immune system, the system does not provide long-lasting immunity to the host. Innate immune systems provide immediate defense against infection, and are found in all classes of plant and animal life.  - A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.  - The bloodbrain barrier (BBB) is a highly selective semipermeable membrane barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system (CNS). The bloodbrain barrier is formed by brain endothelial cells, which are connected by tight junctions. The bloodbrain barrier allows the passage of water, some gases, and lipid-soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function. Furthermore, it prevents the entry of lipophilic potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein. Astrocytes have been claimed to be necessary to create the bloodbrain barrier. A few regions in the brain, including the circumventricular organs, do not have a bloodbrain barrier.  - A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term "molecule" is often used less strictly, also being applied to polyatomic ions.  - Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.  - The adaptive immune system, also known as the acquired immune system or, more rarely, as the specific immune system, is a subsystem of the overall immune system that is composed of highly specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The adaptive immune system is one of the two main immunity strategies found in vertebrates (the other being the innate immune system). Adaptive immunity creates immunological memory after an initial response to a specific pathogen, and leads to an enhanced response to subsequent encounters with that pathogen. This process of acquired immunity is the basis of vaccination. Like the innate system, the adaptive system includes both humoral immunity components and cell-mediated immunity components.  - The immune system is a host defense system comprising many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue. In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity. In humans, the bloodbrain barrier, bloodcerebrospinal fluid barrier, and similar fluidbrain barriers separate the peripheral immune system from the neuroimmune system which protects the brain.  - Immune response is the immunological response originating from immune system activation by antigens, including immunity to pathogenic microorganisms and its products, as well as autoimmunity to self-antigens allergies, and graft ejections. In this process main cells involved are the T cells, B cells of lymphocytes, and macrophagea. These cells produce lymphokines that influence the other host cells activities. B cels mature to produce immunoglobulins or antibodies, that react with antigens. At same time, macrophages are processing the antigens into immunogenic units which stimulate B lymphocites to differentiation into antibody secreting plasma cells, stimulating the T cells to realise lymphokines. Complement is a group of normal serum proteins to aim immunity by becoming activated form as result of antigen-antibody interaction. The first contact with any antigen sensitize individual affected and promote the "primary immune response". Next of the sensitized individuals with same antigen result in a more rapid and massive reaction, called the "secondary immune response" ("booster response" or the "anamnestic reaction") . It is most expressed in the level of circulating serum antibodies.  - Immunology is a branch of biology that covers the study of immune systems in all organisms. It was the Russian biologist Ilya Ilyich Mechnikov who boosted studies on immunology, and received the Nobel Prize in 1908 for his work. He jabbed the thorn of a rose on a starfish and noted that, 24 hours later, cells were surrounding the tip. It was an active response of the body, trying to maintain its integrity. It was Mechnikov who first observed the phenomenon of phagocytosis, in which the body defends itself against a foreign body, and coined the term. It charts, measures, and contextualizes the: physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as autoimmune diseases, hypersensitivities, immune deficiency, and transplant rejection); the physical, chemical and physiological characteristics of the components of the immune system "in vitro", "in situ," and "in vivo". Immunology has applications in numerous disciplines of medicine, particularly in the fields of organ transplantation, oncology, virology, bacteriology, parasitology, psychiatry, and dermatology.  - In immunology, an antigen is a molecule capable of inducing an immune response on the part of the host organism, though sometimes antigens can be part of the host itself. In other words, an antigen is any substance that causes an immune system to produce antibodies against it. Each antibody is specifically produced by the immune system to match an antigen after cells in the immune system come into contact with it; this allows a precise identification of the antigen and the initiation of a tailored response. The antibody is said to "match" the antigen in the sense that it can bind to it thanks to adaptations performed to a region of the antibody; because of this, many different antibodies can be produced, with specificity to bind many different antigens while sharing the same basic structure. In most cases, an antibody can only bind one specific antigen; in some instances, however, antibodies may bind more than one antigen.  - Humoral immunity or humoural immunity is the aspect of immunity that is mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides. Humoral immunity is so named because it involves substances found in the humors, or body fluids. It contrasts with cell-mediated immunity. Its aspects involving antibodies are often called antibody-mediated immunity.  - A T cell, or T lymphocyte, is a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called "T cells" because they mature in the thymus from thymocytes (although some also mature in the tonsils). The several subsets of T cells each have a distinct function. The majority of human T cells rearrange their alpha and beta chains on the cell receptor and are termed alpha beta T cells ( T cells) and are part of the adaptive immune system. Specialized gamma delta T cells, (a small minority of T cells in the human body, more frequent in ruminants), have invariant T cell receptors with limited diversity, that can effectively present antigens to other T cells and are considered to be part of the innate immune system.  - A disease is a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism. The study of disease is called pathology which includes the causal study of etiology. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens, or it may be caused by internal dysfunctions particularly of the immune system such as an immunodeficiency, or a hypersensitivity including allergies and autoimmunity.  - In biology, an organism is any contiguous living system, such as an animal, plant, fungus, archaeon, or bacterium. All known types of organisms are capable of some degree of response to stimuli, reproduction, growth and development and homeostasis. An organism consists of one or more cells; when it has one cell it is known as a unicellular organism; and when it has more than one it is known as a multicellular organism. Most unicellular organisms are of microscopic scale and are thus loosely described as microorganisms. Humans are multicellular organisms composed of many trillions of cells grouped into specialized tissues and organs.  - Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.  - The neuroimmune system is a system of structures and processes involving the biochemical and electrophysiological interactions between the nervous system and immune system which protect neurons from pathogens. It serves to protect neurons against disease by maintaining selectively permeable barriers (e.g., the bloodbrain barrier and bloodcerebrospinal fluid barrier), mediating neuroinflammation and wound healing in damaged neurons, and mobilizing host defenses against pathogens.    After reading the paragraphs above, we are interested in knowing the entity with which 'dendritic cell' exhibits the relationship of 'subclass of'. Find the answer from the choices below.  Choices: - agent  - animal  - antigen  - aspect  - bacteria  - being  - biochemistry  - biology  - body fluid  - brain  - branch  - cell  - charge  - chemistry  - condition  - disease  - fluid  - function  - group  - healing  - hypersensitivity  - immune system  - ion  - life  - medicine  - membrane  - molecule  - nobel prize  - organ  - organic chemistry  - own  - pathogen  - pathology  - phenomenon  - reproduction  - scale  - semipermeable membrane  - sense  - structure  - study  - system  - term  - time  - transport  - vaccination  - variety  - via  - virus  - white blood cell  - wound
The answer is:
white blood cell