Immune & Infectious

Anaphylaxis is a rapid systemic hypersensitivity reaction in which mast cell degranulation produces widespread vasodilation, increased capillary permeability and bronchoconstriction. It is recognized by involvement of more than one system — skin with urticaria, flushing and angiedema; respiratory with stridor, wheeze and a sensation of throat closing; cardiovascular with hypotension and tachycardia; and gastrointestinal with cramping and vomiting. Treatment is epinephrine given intramuscularly into the anterolateral thigh, repeated every five to fifteen minutes as needed, alongside removal of the trigger, airway support, high-flow oxygen, supine positioning with the legs raised where blood pressure allows, and rapid fluid resuscitation. Antihistamines relieve the cutaneous symptoms and corticosteroids reduce the biphasic late-phase reaction that can occur hours later, which is why clients are observed after apparent recovery. Delayed epinephrine is the factor most consistently associated with fatal outcomes.

Allergy skin testing identifies IgE-mediated sensitivity by introducing small amounts of allergen into the skin and observing for a wheal-and-flare response, read at around fifteen to twenty minutes. Percutaneous prick testing is performed first, with intradermal testing used for greater sensitivity where prick testing is negative. Preparation requires withholding medications that suppress the response: antihistamines for several days to a week depending on the agent, and topical corticosteroids at the test site, while systemic corticosteroids at usual doses generally have less effect. A positive and a negative control are applied to confirm the skin is capable of reacting and is not reacting non-specifically. The procedure carries a real risk of systemic reaction including anaphylaxis, so resuscitation equipment and epinephrine are immediately available and the client is observed for twenty to thirty minutes afterwards. Beta-blockers antagonize the response to epinephrine and complicate the treatment of anaphylaxis, so their use is identified and discussed beforehand. Sites are mapped and documented so reactions are attributed correctly, and results are interpreted alongside history rather than alone, since sensitization does not always equal clinical allergy.

HIV diagnosis requires a confirmatory antibody test after a reactive screen; CD4+ count and viral load stage and monitor established infection.

Hypersensitivity reactions are classified by immune mechanism, and the mechanism determines both the timing of onset and the effective treatment.

Latex proteins cross-react with several foods, and repeated exposure escalates reaction severity, so management requires complete avoidance.

Early sepsis causes vasodilation and compensation, so mental status, respiratory rate and urine output change before blood pressure does.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, and its recognition depends on noticing physiological deterioration in a client known or suspected to be infected. Warning features include temperature above 38 or below 36 degrees, heart rate above 90, respiratory rate above 20, altered mental status, systolic blood pressure below 100 or a substantial fall from the client's own baseline, reduced urine output, and raised lactate. Older adults and immunocompromised clients may present atypically, with confusion or hypothermia rather than fever. Management follows a time-limited bundle: obtain blood cultures and lactate, give broad-spectrum antibiotics, begin crystalloid resuscitation for hypotension or raised lactate, and reassess, with vasopressors added where fluid alone does not restore perfusion. Delay in antibiotics is consistently associated with increased mortality. Source control matters and follows stabilization, and indwelling devices such as urinary catheters are frequent sources, which is why their necessity is reviewed daily.

The spleen clears encapsulated bacteria from blood, so asplenia creates a specific and rapid sepsis risk.

Tumor necrosis factor inhibitors suppress the immune response that contains latent tuberculosis, so screening precedes therapy and infection signs become unreliable.

Falling CD4 counts allow ordinarily harmless organisms to cause serious infection, so prevention centers on food, animal and water exposure.

The absolute neutrophil count determines infection risk in a client receiving chemotherapy: below 1,000 the risk is meaningful, below 500 it is severe, and the nadir typically falls seven to fourteen days after a cycle. Without neutrophils the inflammatory response that produces the familiar signs of infection cannot occur, so localizing findings may be absent and fever alone defines the emergency. Febrile neutropenia is managed by immediate notification, blood cultures from peripheral and central sites, cultures of urine and any suspect site, and broad-spectrum intravenous antibiotics as soon as possible, with time to first antibiotic dose being the measure that tracks survival. Antipyretics are avoided before assessment because they conceal the finding. Protective measures reduce the chance of acquiring infection and belong to the preceding days rather than to this moment: meticulous hand hygiene by everyone entering, avoidance of anyone unwell, no fresh flowers or standing water, careful oral and perineal hygiene, and no rectal temperatures, suppositories or enemas, which breach mucosa. Growth factors may be given to shorten the neutropenic period.

Systemic lupus erythematosus is a chronic autoimmune disease with periods of flare and remission, affecting skin, joints, kidneys, blood, serosal membranes, heart, lungs and nervous system. Presentation commonly includes fatigue, fever, arthralgia and arthritis, photosensitivity, the malar butterfly rash across cheeks and nose sparing the nasolabial folds, discoid lesions, oral ulcers, Raynaud phenomenon, serositis producing pleuritic or pericardial pain, and hematological changes. Lupus nephritis is the complication that most influences prognosis, may be clinically silent early, and is monitored with urinalysis for protein and casts, renal function and blood pressure. Infection is a leading cause of mortality, reflecting both the disease and immunosuppressive therapy. Management includes hydroxychloroquine as a maintenance agent for most clients, corticosteroids and immunosuppressants for active disease, and non-steroidal anti-inflammatories for musculoskeletal symptoms. Teaching covers rigorous photoprotection, since ultraviolet exposure triggers systemic flares as well as cutaneous ones; energy conservation and pacing; adherence to maintenance therapy during remission; prompt reporting of fever; contraception and pregnancy planning, since pregnancy is timed to periods of quiescence; and regular monitoring.

The spleen clears encapsulated bacteria from blood, so asplenia creates a specific and rapid sepsis risk.

Weight loss in advanced HIV infection is multifactorial: reduced intake from oral and esophageal candidiasis, nausea, fatigue, depression and medication effects; malabsorption from opportunistic gastrointestinal infection and enteropathy; and increased metabolic demand from chronic immune activation and intercurrent infection. Wasting specifically denotes loss of lean body mass and is associated with worse outcomes independent of viral load. Nutritional care therefore aims at energy and protein density rather than volume, with small frequent meals, oral supplements where needed, and treatment of the reversible causes — oral examination at every opportunity, since candidiasis is common and readily treated. Diet is individualized to symptoms rather than following general wellness patterns, so fat and fiber are moderated where diarrhea or malabsorption exists, and lactose is often poorly tolerated. Food safety teaching matters because immunosuppression raises both the likelihood and the severity of foodborne illness, and covers thorough cooking, avoidance of unpasteurized dairy and juice, careful produce washing and safe storage. Weight, intake and albumin trends are monitored, and antiretroviral adherence remains the intervention with the largest effect on nutritional status.

Anaphylaxis is a rapid systemic hypersensitivity reaction in which mast cell degranulation produces widespread vasodilation, increased capillary permeability and bronchoconstriction. It is recognized by involvement of more than one system — skin with urticaria, flushing and angiedema; respiratory with stridor, wheeze and a sensation of throat closing; cardiovascular with hypotension and tachycardia; and gastrointestinal with cramping and vomiting. Treatment is epinephrine given intramuscularly into the anterolateral thigh, repeated every five to fifteen minutes as needed, alongside removal of the trigger, airway support, high-flow oxygen, supine positioning with the legs raised where blood pressure allows, and rapid fluid resuscitation. Antihistamines relieve the cutaneous symptoms and corticosteroids reduce the biphasic late-phase reaction that can occur hours later, which is why clients are observed after apparent recovery. Delayed epinephrine is the factor most consistently associated with fatal outcomes.

Allergy skin testing identifies IgE-mediated sensitivity by introducing small amounts of allergen into the skin and observing for a wheal-and-flare response, read at around fifteen to twenty minutes. Percutaneous prick testing is performed first, with intradermal testing used for greater sensitivity where prick testing is negative. Preparation requires withholding medications that suppress the response: antihistamines for several days to a week depending on the agent, and topical corticosteroids at the test site, while systemic corticosteroids at usual doses generally have less effect. A positive and a negative control are applied to confirm the skin is capable of reacting and is not reacting non-specifically. The procedure carries a real risk of systemic reaction including anaphylaxis, so resuscitation equipment and epinephrine are immediately available and the client is observed for twenty to thirty minutes afterwards. Beta-blockers antagonize the response to epinephrine and complicate the treatment of anaphylaxis, so their use is identified and discussed beforehand. Sites are mapped and documented so reactions are attributed correctly, and results are interpreted alongside history rather than alone, since sensitization does not always equal clinical allergy.

Hypersensitivity reactions are classified by immune mechanism, and the mechanism determines both the timing of onset and the effective treatment.

Latex proteins cross-react with several foods, and repeated exposure escalates reaction severity, so management requires complete avoidance.

Latex allergy cross-reacts with several foods — most characteristically banana, avocado, kiwi and chestnut. The proteins are similar enough for the immune system to treat them alike, so a client reporting reactions to those foods should be assumed at risk of latex allergy until assessed. The clinically important exposures in a hospital are gloves, urinary catheters, tourniquets, blood pressure cuffs, adhesive dressings and some medication vial stoppers, and reactions range from contact dermatitis to anaphylaxis. Latex precautions are instituted and flagged before any procedure, and latex-free equipment is used throughout.

The absolute neutrophil count determines infection risk in a client receiving chemotherapy: below 1,000 the risk is meaningful, below 500 it is severe, and the nadir typically falls seven to fourteen days after a cycle. Without neutrophils the inflammatory response that produces the familiar signs of infection cannot occur, so localizing findings may be absent and fever alone defines the emergency. Febrile neutropenia is managed by immediate notification, blood cultures from peripheral and central sites, cultures of urine and any suspect site, and broad-spectrum intravenous antibiotics as soon as possible, with time to first antibiotic dose being the measure that tracks survival. Antipyretics are avoided before assessment because they conceal the finding. Protective measures reduce the chance of acquiring infection and belong to the preceding days rather than to this moment: meticulous hand hygiene by everyone entering, avoidance of anyone unwell, no fresh flowers or standing water, careful oral and perineal hygiene, and no rectal temperatures, suppositories or enemas, which breach mucosa. Growth factors may be given to shorten the neutropenic period.

Early sepsis causes vasodilation and compensation, so mental status, respiratory rate and urine output change before blood pressure does.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, and its recognition depends on noticing physiological deterioration in a client known or suspected to be infected. Warning features include temperature above 38 or below 36 degrees, heart rate above 90, respiratory rate above 20, altered mental status, systolic blood pressure below 100 or a substantial fall from the client's own baseline, reduced urine output, and raised lactate. Older adults and immunocompromised clients may present atypically, with confusion or hypothermia rather than fever. Management follows a time-limited bundle: obtain blood cultures and lactate, give broad-spectrum antibiotics, begin crystalloid resuscitation for hypotension or raised lactate, and reassess, with vasopressors added where fluid alone does not restore perfusion. Delay in antibiotics is consistently associated with increased mortality. Source control matters and follows stabilization, and indwelling devices such as urinary catheters are frequent sources, which is why their necessity is reviewed daily.

HIV diagnosis requires a confirmatory antibody test after a reactive screen; CD4+ count and viral load stage and monitor established infection.

Falling CD4 counts allow ordinarily harmless organisms to cause serious infection, so prevention centers on food, animal and water exposure.

Weight loss in advanced HIV infection is multifactorial: reduced intake from oral and esophageal candidiasis, nausea, fatigue, depression and medication effects; malabsorption from opportunistic gastrointestinal infection and enteropathy; and increased metabolic demand from chronic immune activation and intercurrent infection. Wasting specifically denotes loss of lean body mass and is associated with worse outcomes independent of viral load. Nutritional care therefore aims at energy and protein density rather than volume, with small frequent meals, oral supplements where needed, and treatment of the reversible causes — oral examination at every opportunity, since candidiasis is common and readily treated. Diet is individualized to symptoms rather than following general wellness patterns, so fat and fiber are moderated where diarrhea or malabsorption exists, and lactose is often poorly tolerated. Food safety teaching matters because immunosuppression raises both the likelihood and the severity of foodborne illness, and covers thorough cooking, avoidance of unpasteurized dairy and juice, careful produce washing and safe storage. Weight, intake and albumin trends are monitored, and antiretroviral adherence remains the intervention with the largest effect on nutritional status.

Tumor necrosis factor inhibitors suppress the immune response that contains latent tuberculosis, so screening precedes therapy and infection signs become unreliable.

Systemic lupus erythematosus is a chronic autoimmune disease with periods of flare and remission, affecting skin, joints, kidneys, blood, serosal membranes, heart, lungs and nervous system. Presentation commonly includes fatigue, fever, arthralgia and arthritis, photosensitivity, the malar butterfly rash across cheeks and nose sparing the nasolabial folds, discoid lesions, oral ulcers, Raynaud phenomenon, serositis producing pleuritic or pericardial pain, and hematological changes. Lupus nephritis is the complication that most influences prognosis, may be clinically silent early, and is monitored with urinalysis for protein and casts, renal function and blood pressure. Infection is a leading cause of mortality, reflecting both the disease and immunosuppressive therapy. Management includes hydroxychloroquine as a maintenance agent for most clients, corticosteroids and immunosuppressants for active disease, and non-steroidal anti-inflammatories for musculoskeletal symptoms. Teaching covers rigorous photoprotection, since ultraviolet exposure triggers systemic flares as well as cutaneous ones; energy conservation and pacing; adherence to maintenance therapy during remission; prompt reporting of fever; contraception and pregnancy planning, since pregnancy is timed to periods of quiescence; and regular monitoring.

Falling CD4 counts allow ordinarily harmless organisms to cause serious infection, so prevention centers on food, animal and water exposure.

Latex proteins cross-react with several foods, and repeated exposure escalates reaction severity, so management requires complete avoidance.

Tumor necrosis factor inhibitors suppress the immune response that contains latent tuberculosis, so screening precedes therapy and infection signs become unreliable.

Hypersensitivity reactions are classified by immune mechanism, and the mechanism determines both the timing of onset and the effective treatment.

Contact precautions work by keeping the organism inside the room — on hands, on equipment and on items. Gown and gloves are worn on entry and removed before leaving; equipment such as stethoscopes, blood pressure cuffs and thermometers is dedicated to the client or disinfected between uses; and items are not carried out into shared areas. Contact precautions apply to organisms spread by direct or indirect contact, including MRSA, VRE, Clostridioides difficile and scabies, with C. difficile additionally requiring soap and water rather than alcohol rub, because spores resist alcohol. Precautions restrict transmission, not affection.

Latex allergy cross-reacts with several foods — most characteristically banana, avocado, kiwi and chestnut. The proteins are similar enough for the immune system to treat them alike, so a client reporting reactions to those foods should be assumed at risk of latex allergy until assessed. The clinically important exposures in a hospital are gloves, urinary catheters, tourniquets, blood pressure cuffs, adhesive dressings and some medication vial stoppers, and reactions range from contact dermatitis to anaphylaxis. Latex precautions are instituted and flagged before any procedure, and latex-free equipment is used throughout.

Latex allergy cross-reacts with several foods — most characteristically banana, avocado, kiwi and chestnut. The proteins are similar enough for the immune system to treat them alike, so a client reporting reactions to those foods should be assumed at risk of latex allergy until assessed. The clinically important exposures in a hospital are gloves, urinary catheters, tourniquets, blood pressure cuffs, adhesive dressings and some medication vial stoppers, and reactions range from contact dermatitis to anaphylaxis. Latex precautions are instituted and flagged before any procedure, and latex-free equipment is used throughout.

The absolute neutrophil count determines infection risk in a client receiving chemotherapy: below 1,000 the risk is meaningful, below 500 it is severe, and the nadir typically falls seven to fourteen days after a cycle. Without neutrophils the inflammatory response that produces the familiar signs of infection cannot occur, so localizing findings may be absent and fever alone defines the emergency. Febrile neutropenia is managed by immediate notification, blood cultures from peripheral and central sites, cultures of urine and any suspect site, and broad-spectrum intravenous antibiotics as soon as possible, with time to first antibiotic dose being the measure that tracks survival. Antipyretics are avoided before assessment because they conceal the finding. Protective measures reduce the chance of acquiring infection and belong to the preceding days rather than to this moment: meticulous hand hygiene by everyone entering, avoidance of anyone unwell, no fresh flowers or standing water, careful oral and perineal hygiene, and no rectal temperatures, suppositories or enemas, which breach mucosa. Growth factors may be given to shorten the neutropenic period.

Weight loss in advanced HIV infection is multifactorial: reduced intake from oral and esophageal candidiasis, nausea, fatigue, depression and medication effects; malabsorption from opportunistic gastrointestinal infection and enteropathy; and increased metabolic demand from chronic immune activation and intercurrent infection. Wasting specifically denotes loss of lean body mass and is associated with worse outcomes independent of viral load. Nutritional care therefore aims at energy and protein density rather than volume, with small frequent meals, oral supplements where needed, and treatment of the reversible causes — oral examination at every opportunity, since candidiasis is common and readily treated. Diet is individualized to symptoms rather than following general wellness patterns, so fat and fiber are moderated where diarrhea or malabsorption exists, and lactose is often poorly tolerated. Food safety teaching matters because immunosuppression raises both the likelihood and the severity of foodborne illness, and covers thorough cooking, avoidance of unpasteurized dairy and juice, careful produce washing and safe storage. Weight, intake and albumin trends are monitored, and antiretroviral adherence remains the intervention with the largest effect on nutritional status.

Contact precautions work by keeping the organism inside the room — on hands, on equipment and on items. Gown and gloves are worn on entry and removed before leaving; equipment such as stethoscopes, blood pressure cuffs and thermometers is dedicated to the client or disinfected between uses; and items are not carried out into shared areas. Contact precautions apply to organisms spread by direct or indirect contact, including MRSA, VRE, Clostridioides difficile and scabies, with C. difficile additionally requiring soap and water rather than alcohol rub, because spores resist alcohol. Precautions restrict transmission, not affection.

Contact precautions work by keeping the organism inside the room — on hands, on equipment and on items. Gown and gloves are worn on entry and removed before leaving; equipment such as stethoscopes, blood pressure cuffs and thermometers is dedicated to the client or disinfected between uses; and items are not carried out into shared areas. Contact precautions apply to organisms spread by direct or indirect contact, including MRSA, VRE, Clostridioides difficile and scabies, with C. difficile additionally requiring soap and water rather than alcohol rub, because spores resist alcohol. Precautions restrict transmission, not affection.

Early sepsis causes vasodilation and compensation, so mental status, respiratory rate and urine output change before blood pressure does.