| Millions of Canadians suffer from allergies and asthma. | | | | mycobacteria, fungi, parasites, and, often, |
| When your immune system identifies a normally | | | | mucocutaneous candidiasis. Undesirable consequences |
| harmless material as a threat, it can set off | | | | of delayed-type hypersensitivity (DTH) reactions |
| symptoms like sniffles, sneezes, rashes or breathing | | | | include illness such as contact dermatitis and allograft |
| problems. | | | | rejection. |
| Although allergies and colds have similar symptoms, | | | | Examples of DTH reactions are contact dermatitis |
| there are some telltale signs that can help you | | | | (eg, poison ivy rash), tuberculin skin test reactions, |
| differentiate between them. If you aren't sure | | | | granulomatous inflammation (eg, sarcoidosis, Crohn |
| whether you have allergies or just a cold, ask your | | | | disease), allograft rejection, graft versus host |
| health professional. Your pharmacist or doctor can | | | | disease, and autoimmune hypersensitivity reactions. |
| help determine the cause of your symptoms and | | | | Of note, the Rhus genus of plants, which includes |
| recommend appropriate treatment. | | | | poison ivy, poison oak, and poison sumac, all cause |
| Experts think that 1-2 percent of Canadians have | | | | identical rashes. |
| serious allergies to food, insects, medications, latex, | | | | The cellular events that result in delayed |
| and exercise. These allergies are potentially | | | | hypersensitivity reactions primarily involve T cells and |
| life-threatening emergencies that require immediate | | | | macrophages. First, local immune and inflammatory |
| medical attention. | | | | responses at the site of foreign antigen up-regulate |
| A person experiencing a serious allergic reaction may | | | | endothelial cell adhesion molecule expression, |
| have difficulty breathing, throat swelling, skin redness | | | | promoting the accumulation of leukocytes at the |
| or itching, and an irregular heartbeat or palpitations. In | | | | tissue site. The antigen is engulfed by macrophages |
| most cases, it is recommended that people with an | | | | and monocytes and is presented to a T cell that has |
| identified serious allergy wear a MedicAlert bracelet | | | | a specific receptor for that antigen. Macrophages |
| and carry an EpiPen, which is an injection device that | | | | secrete interleukin (IL)1, IL-2, IL-6, and other |
| contains epinephrine. | | | | lymphokines. Cytotoxic T cells can also be activated. |
| A recent study showed that two out of three | | | | The recruited macrophages can form giant cells. The |
| parents were unsure of how to use their child's | | | | characteristic histologic appearance of the |
| EpiPen, and almost half did not even carry their | | | | macrophage T-cell infiltrate is a granuloma. This type |
| EpiPen with them at all times. If you or a family | | | | of infiltrate in the tissue is called granulomatous |
| member have a serious allergy, talk to your | | | | inflammation. |
| pharmacist or doctor, and make sure you know how | | | | Several variants of DTH exist, and their precise |
| to recognize all the signs of a potentially | | | | pathophysiologic mechanisms are slightly different. For |
| life-threatening reaction so that you know exactly | | | | example, in contact hypersensitivity reactions, the |
| what to do if the time ever comes. | | | | epidermis is involved; in pulmonary tuberculosis (TB), |
| Delayed hypersensitivity reactions are inflammatory | | | | lung tissue is involved. |
| reactions initiated by mononuclear leukocytes. The | | | | Delayed hypersensitivity reactions are normal |
| term delayed is used to differentiate a secondary | | | | physiological events. Anything that alters these |
| cellular response, which appears 48-72 hours after | | | | normal events can lead to multiple opportunistic |
| antigen exposure, from an immediate hypersensitivity | | | | infections. Immune deficiencies (congenital or |
| response, which generally appears within 12 minutes | | | | acquired) and immunosuppressive agents can alter |
| of an antigen challenge. These reactions are mediated | | | | this normal response.he cellular events that result in |
| by T cells and monocytes/macrophages rather than | | | | delayed hypersensitivity reactions primarily involve T |
| by antibodies. They are also termed type IV | | | | cells and macrophages. First, local immune and |
| hypersensitivity reactions. | | | | inflammatory responses at the site of foreign antigen |
| Delayed hypersensitivity is a major mechanism of | | | | up-regulate endothelial cell adhesion molecule |
| defense against various intracellular pathogens, | | | | expression, promoting the accumulation of leukocytes |
| including mycobacteria, fungi, and certain parasites, | | | | at the tissue site. The antigen is engulfed by |
| and it occurs in transplant rejection and tumor | | | | macrophages and monocytes and is presented to a |
| immunity. The central role of CD4+ T cells in delayed | | | | T cell that has a specific receptor for that antigen. |
| hypersensitivity manifests in patients with AIDS. | | | | Macrophages secrete IL-1, IL-2, IL-6, and other |
| Because of the loss of CD4+ cells, the host response | | | | lymphokines. Cytotoxic T cells can also be activated. |
| against intracellular pathogens such as Mycobacterium | | | | The recruited macrophages can form giant cells. The |
| tuberculosis is markedly impaired. The bacteria are | | | | characteristic histologic appearance of the |
| engulfed by macrophages but are not killed. | | | | macrophage T-cell infiltrate is a granuloma. This type |
| If T-cell function is abnormal, the patient presents | | | | of infiltrate in the tissue is called granulomatous |
| with opportunistic infections, including infection with | | | | inflammation. |