The body has a generalized group of phagocytic cells that can attack microbes that have made it past the skin. Macrophages and neutrophils are the first cells to respond to an infection. Monocytes will later migrate from the bloodstream into the body tissues and phagocytize pathogens. T-cells are part of the acquired immune system and are only present after a specific pathogen had been previously encountered in the body.

Natural passive immunity is conveyed from mother to child in-utero or through colostrum in breast milk.  Natural passive immunity provides temporary immunity to many diseases.

Natural active immunity occurs when an individual develops a disease as a result of being exposed to a live pathogen, and acquires immunity to that pathogen as a result.

Artificial active immunity is acquired as a result of intentional exposure to a pathogen, as in a vaccination.

Artificial passive immunity occurs when antibodies are transferred from one person to another. Immediate short-term protection may be conveyed to immune-compromised patients, such as chemotherapy recipients, by this mean.

Essentially, active immunity requires exposure to a live pathogen; passive immunity does not (only antibodies). Artificial immunity requires intervention in the form of a vaccine or medical care, while natural immunity occurs unintentionally through exposure.

Toll-like receptors (TLRs) are a family of receptors found within innate immune antigen-presenting cells such as dendritic cells, monocytes, and macrophages. These receptors recognize specific elements of various infectious agents such as lipopolysaccharides, DNA, and RNA. Binding and activation of these receptors stimulates inflammatory responses and CD4/CD8 T-cell responses to drive an effective immune response.

TLRs do not control B-cell clonal selection, the process by which B-cells replicate to amplify the production of a certain antibody.

Innate immunity is a generalized form of protection against pathogens in the body. The cells of innate immunity generally attack all types of invasive agents and do not interact with antibody production.

Neutrophils, eosinophils, and macrophages are all generalized leukocytes that are present in the body. Neutrophils, basophils, and eosinophils are the primary granulocytes, all of which are involved in innate immunity. Macrophages are differentiated monocytes, capable of phagocytosis against non-specific invaders.

Plasma cells are differentiated B-lymphocytes. They release antibodies into the bloodstream that are specific for a given pathogen. As a result, plasma cells are only present following a specific infection. They are a crucial part of the adaptive immune response, but are not involved in innate immunity.