A look at immunologic disorders
A normally functioning immune system guards against the effects of invasion by microorganisms and maintains equilibrium within the body by governing degradation and removal of damaged cells. When the immune system functions abnormally, physiologic effects can be devastating.
Immunologic disorders can result from or cause problems in other systems. This makes accurate assessment and intervention both crucial and challenging.
Besides endangering the patient’s health—or even his life— some immunologic disorders pose a serious health risk to caregivers. This is yet another of the many challenges you’ll face when caring for a patient with an immunologic disorder.
Anatomy and physiology
The immune system consists of specialized blood cells (lymphocytes and macrophages) and specialized structures, including the lymph nodes, spleen, thymus, bone marrow, tonsils, adenoids, and appendix.
The blood is an important part of this protective system. Although the blood and immune system are distinct entities, they’re closely related. Their cells share a common origin in the bone marrow, and the immune system uses the bloodstream to transport its components to the site of an invasion.
Immunity refers to the body’s capacity to resist invading organisms and toxins, thus preventing tissue and organ damage. The cells and organs of the immune system perform that function.
Scavengers on surveillance
The immune system recognizes, responds to, and eliminates foreign substances (antigens), such as bacteria, fungi, viruses, and parasites. It also preserves the internal environment by scavenging dead or damaged cells and by performing surveillance.
To perform these functions efficiently, the immune system uses three basic defense strategies:
physical and chemical barriers to infection
Breaking through the barriers
Physical barriers, such as the skin and mucous membranes, prevent most organisms from invading the body. Organisms that penetrate this first barrier simultaneously trigger the inflammatory and immune responses. Both responses involve stem cells— primitive cells in the bone marrow from which all types of blood cells derive.
Types of immunity
In general host defenses, all foreign substances elicit the same response. In contrast, particular microorganisms or molecules activate specific immune responses, and initially can involve specialized sets of immune cells. These specific responses are classified as either humoral or cell-mediated immunity. Lymphocytes (B cells and T cells) produce the responses.
In the humoral response, an invading antigen causes B cells to divide and differentiate into plasma cells. Each plasma cell, in turn, produces and secretes large amounts of antigen-specific immunoglobulins (Ig) into the bloodstream.
Mind your Igs
Immunoglobulins exist in five types—IgA, IgD, IgE, IgG, and IgM.
Each type serves a particular function:
• IgA, IgG, and IgM guard against viral and bacterial invasion.
• IgD acts as an antigen receptor of B cells.
• IgE causes an allergic response.
Thanks for the complement
Indispensable to humoral immunity, the complement system consists of about 25 enzymes that “complement” the work of antibodiesby aiding phagocytosis or destroying bacterial cells (through puncture of their cell membranes).
Cell-mediated immunity protects the body against bacterial, viral, and fungal infections. It also resists transplanted cells and tumor cells. In the cell-mediated immune response, a type of scavenger cell called a macrophage processes the antigen, which is then presented to T cells.
Accurately assessing the immune system can challenge your skills because immune disorders commonly cause vague symptoms, such as fatigue or dyspnea. Initially, these symptoms may seem to be related to other body systems.
Begin your assessment with a thorough history. Because the immune system affects all body functions, be sure to investigate the patient’s overall health.
Current health status
Among patients with immunologic disorders, common complaints include fatigue or lack of energy, light-headedness, frequent bruising, and slow wound healing.
Ask these questions to elicit details about your patient’s current illness:
• Have you noticed enlarged lymph nodes?
• Have you experienced weakness or joint pain? If so, when did you first notice the problem? Does it affect one side of your body or both sides?
• Have you recently had a rash, abnormal bleeding, or a slow healing sore?
• Have you experienced vision disturbances, fever, or changes in elimination patterns?
• Have you felt more tired recently? If so, when did it start?
Previous health status
Explore the patient’s previous major illnesses, recurrent minor illnesses, accidents or injuries, surgical procedures, and allergies. Ask if he has had a procedure that could affect the immune system, such as a blood transfusion or an organ transplant.
Family and social history
Find out if the patient has a family history of cancer or hematologic or immune disorders. Ask about his home and work environments to help determine if he’s being exposed to hazardous chemicals or other agents.
The effects of immune disorders are far-reaching and may materialize in several body systems. Pay special attention to the skin, hair, nails, and mucous membranes.
• Observe for pallor, cyanosis (blue-tinged skin), and jaundice. Also check for erythema (redness), indicating a local inflammation, and plethora (a red, florid complexion).
• Evaluate skin integrity. Note signs and symptoms of inflammation or infection, such as redness, swelling, heat, tenderness, poor wound healing, wound drainage, induration (tissue hardening), and lesions.
• Check for rash, and note its distribution.
• Observe hair texture and distribution, noting alopecia (hair loss) on the arms, legs, or head.
After inspection, palpate the peripheral pulses, which should be symmetrical and regular. Next, palpate the abdomen, noting enlarged organs and tenderness, and then the joints, checking for swelling, tenderness, and pain.
Noting the nodes
Palpate the superficial lymph nodes in the head and neck and in the axillary, epitrochlear, inguinal, and popliteal areas. If palpation reveals an enlarged node or other abnormalities, note the node’s location, size, shape, surface, consistency, symmetry, mobility, color, tenderness, temperature, pulsations, and vascularity.
Next, percuss the anterior, lateral, and posterior thorax, comparing one side with the other. A dull sound indicates consolidation, which may occur with pneumonia. Hyperresonance (increased percussion sounds) may result from trapped air, as from bronchial asthma.
Finally, auscultate over the lungs to check for adventitious (abnormal) sounds. Wheezing suggests asthma or an allergic response. Crackles may signal a respiratory tract infection such as pneumonia.
Sounding it out
Auscultate for heart sounds over the precordium. Normal auscultation reveals only the first and second heart sounds (lub-dub). Next, auscultate the abdomen for bowel sounds. With autoimmune disorders that cause diarrhea, bowel sounds increase. With scleroderma (skin hardening and thickening, with degeneration of connective tissue) and other autoimmune disorders that cause constipation, bowel sounds decrease.
Two commonly ordered studies to evaluate the immune response are general cellular tests (which help diagnose immunodeficiency disorders) and delayed hypersensitivity skin tests (which evaluate the cell-mediated immune response).
General cellular tests
General cellular tests, such as T- and B-lymphocyte assays, help diagnose primary and secondary immunodeficiency disorders.
T- and B-lymphocyte surface marker assays
Surface marker assays identify specific cells involved in the immune response and examine the balance between the regulatory activities of several interacting cell types—notably, T-helper and T-suppressor cells. These tests use highly specific monoclonal antibodies to define levels of lymphocyte differentiation and to analyze both normal and malignant cells.
Plethora of purposes
The results of T- and B-lymphocyte surface marker assays help to:
• assess immunocompetence in chronic infections
• evaluate immunodeficiencies
• classify lymphocytic leukemia, lymphoma, and immunodeficiency diseases such as acquired immunodeficiency syndrome (AIDS)
• identify immunoregulation associated with autoimmune disorders
• diagnose disorders marked by abnormal numbers and percentages of T-helper cells, T-suppressor cells, and B lymphocytes.
• Inform the patient that the test requires a blood sample.
• As ordered, perform a venipuncture. Send the blood sample to the laboratory immediately to ensure viable lymphocytes. The sample must not be refrigerated or frozen. Apply pressure to the venipuncture site until bleeding stops.
• Many patients with T- and B-cell changes have a compromised immune system, so be sure to keep the veni puncture site clean and dry.
Delayed hypersensitivity skin tests
Delayed hypersensitivity skin tests evaluate the cell-mediated immune response. They include intradermal skin tests and scratch and puncture allergy tests.
Intradermal skin tests
For intradermal skin tests, recall antigens (antigens to which the patient may have been previously sensitized) are injected into the superficial skin layer with a needle and syringe or a sterile four-pronged lancet.
TB or not TB?
Tuberculin skin tests (such as the tine or Mantoux) produce a delayed hypersensitivity reaction in patients with active or dormant tuberculosis (TB).
Recalling past antigens
Recall antigen tests for Candida, tetanus, and mumps induce depressed or negative delayed hypersensitivity reactions in patients with infections and immunodeficiencies. Recall antigen tests induce positive delayed hypersensitivity reactions in patients who can maintain a nonspecific inflammatory response to the antigen.
• Tell the patient when he can expect a reaction to appear (usually after 2 days). Check his history for hypersensitivity to the test antigens and for previous reactions to a skin test.
• Using alcohol, clean the volar surface (palm side) of the arm, about 2 or 3 fingerbreadths distal to the antecubital space (triangle of the elbow) to protect the wheal from potential infection. You may also clean the area with acetone to remove skin oils that may interfere with test results.
• Make sure the test site you’ve chosen has adequate subcutaneous tissue and is free from hair and blemishes. Let the skin dry completely before administering the injection to avoid inactivating the antigen.
• Instruct an outpatient to return at the prescribed time to have test results read.
Scratch and puncture allergy tests
Skin scratch and puncture allergy tests evaluate the immune system’s ability to respond to known allergens. A tiny amount of allergen is scratched across or lightly pricked into the skin of a hairless area, such as the scapula, volar surface of the forearm, or anterior surface of the thigh. If the patient has an allergy, the specific allergens he’s allergic to will cause redness and swelling.
Teensy weensy doses
These tests provoke delayed hypersensitivity reactions mediated by T cells. Although minute amounts of test allergens usually can demonstrate an intact immune response, test results may indicate an anergic (diminished or absent) reaction in elderly patients as well as in patients with acute leukemia, Hodgkin’s disease, congenital immunodeficiencies, or overwhelming infections. Scratch and puncture tests are contraindicated in patients with inflammation, skin diseases, or significant immunologic impairment.
• Use the volar surface of the arm to perform the test in an adult; use the upper back in a child.
• After 20 minutes, check for a pale, raised, urticarial area around the puncture or scratch site (wheal), surrounded by a reddened area that’s generally round (flare). This indicates a positive response, meaning a patient is allergic to the specific allergen tested.
• Record the greatest diameter of the wheal and flare for each allergen.
• Have epinephrine available in case of an anaphylactic reaction.
Treatments for immune disorders include drug therapy and bone marrow transplantation. Both may cause additional immunosuppression, so you’ll need to take special precautions to maintain strict asepsis and prevent infection and injury.
Many immune disorders are treated with drugs, so you’ll need to be familiar with the indications, dosages, and nursing considerations for such drugs as:
• antihistamines, which prevent or relieve allergic reactions
• immunosuppressants, used to combat tissue rejection and help control autoimmune disorders
• corticosteroids, which prevent or suppress the cell-mediated immune response and reduce inflammation
• cytotoxic drugs, which kill immunocompetent cells
• adrenergics, which stimulate the sympathetic nervous system.
For certain immune disorders, drugs are the primary treatment. For instance, epinephrine is the drug of choice for treating acute anaphylactic reaction. For other immune disorders, drugs are prescribed to treat associated symptoms.
Besides epinephrine, other drugs used to treat immune disorders include:
• azathioprine (Imuran)
• cyclosporine (Sandimmune)
• cytomegalovirus immune globulin (human)
• didanosine (Videx)
• hepatitis B immune globulin, human
• immune globulin
• lamivudine (Epivir)
• Rho(D) immune globulin
• stavudine (Zerit)
• zidovudine (Retrovir).
Iatrogenic (treatment-induced) immunodeficiency may be a
complicating adverse effect of chemotherapy or other treatment.
In some cases, however, it’s the goal of therapy—for
instance, to suppress immune-mediated tissue damage from
an autoimmune disorder or to prevent rejection of an organ
transplant. To induce immuno deficiency, a patient may
receive various types of immunosuppressant drugs.
Antilymphocyte serum is a powerful nonspecific immunosuppressant that destroys circulating lymphocytes. It reduces T-cell number and function, thus suppressing cell-mediated immunity. It has been used effectively to prevent cell-mediated rejection of tissue grafts or transplants.
Antithymocyte globulin (ATG) causes specific destruction of T lymphocytes. Usually, it’s given immediately before transplantation and continued for some time afterward.
Sickening the serum
Adverse effects of ATG include anaphylaxis and serum sickness. Arising 1 to 2 weeks after ATG injection, serum sickness is marked by fever, malaise, rash, arthralgias and, sometimes, glomerulonephritis or vasculitis.
Corticosteroids are adrenocortical hormones used widely to treat immune-mediated disorders because of their potent antiinflammatory and immunosuppressant effects. They stabilize the vascular membrane, blocking tissue infiltration by neutrophils and monocytes and thus inhibiting inflammation. They also “kidnap” T cells in the bone marrow, causing lymphopenia.
However, because these drugs aren’t toxic to cells, lymphocyte concentration can quickly return to normal within 24 hours after the corticosteroid is withdrawn. Also, corticosteroids seem to inhibit immunoglobulin synthesis and interfere with binding of immunoglobulin to antigen.
Cyclosporine selectively suppresses the proliferation and development of T-helper cells, resulting in depressed cell- mediated immunity.
Cytotoxic drugs kill immunocompetent cells while they’re replicating. Unfortunately, most of these agents aren’t selective, which means they interfere with all rapidly proliferating cells. As a result, they cause depletion of lymphocytes and phagocytes and interfere with lymphocyte synthesis and release of immunoglobulins and lymphokines.
Dicey drug therapy
Cyclophosphamide (Cytoxan), a potent cytotoxic drug commonly used as an immunosuppressant, initially depletes B cells, suppressing humoral immunity. Long-term therapy also depletes T cells, suppressing cell-mediated immunity, too. Cyclophosphamide may be given to patients with systemic lupus erythematosus (SLE), Wegener’s granulomatosis, or certain autoimmune disorders.
Because it nonselectively destroys rapidly dividing cells, the drug can cause severe bone marrow suppression with abnormally low levels of red blood cells, or RBCs (anemia), neutrophils (neutropenia), or platelets (thrombocytopenia). It may also lead to gonadal suppression, resulting in sterility, alopecia, hemorrhagic cystitis, nausea and vomiting, stomatitis, and an increased risk of lymphoproliferative neoplasm.
Other immune busters
Other cytotoxic drugs used to suppress the immune system include:
• azathioprine (Azasan), commonly used in kidney transplant
• methotrexate (Trexall), occasionally used in rheumatoid arthritis and other autoimmune disorders.
Bone marrow transplantation
Patients with certain immune disorders may be candidates for bone marrow transplant. This procedure also is being explored as a treatment of certain hematologic disorders and cancers, such as multiple myeloma and some solid tumors.
Bone up on transplantation
In bone marrow transplantation, bone marrow cells are collected from the patient or another donor and then administered to the patient after his diseased bone marrow is destroyed by chemotherapy or total body radiation. The goal is to allow the patient to resume normal blood cell production.
The preferred treatment for aplastic anemia and severe combined immunodeficiency syndrome (SCID), bone marrow transplantation also is used to treat leukemia patients who are at high risk for relapse or who have undergone high-dose chemotherapy and total body radiation therapy.
Before the procedure, take these steps:
• Inform the patient that bone marrow transplant will deplete his white blood cells (WBCs), putting him at high risk for infection immediately after the procedure. As a safeguard, he’ll be placed in reverse isolation for several weeks.
• Prepare him for the pretransplant regimen, which may include cytotoxic chemotherapy and total body radiation. During this regimen, he should expect adverse reactions, such as parotitis (inflammation or infection of the parotid salivary glands), diarrhea, fever, nausea, vomiting, and signs and symptoms of bone marrow depression (such as fever, fatigue, chills, bruising, and bleeding).
Monitoring and aftercare
During and after the procedure, take these steps:
• During the transfusion, monitor the patient’s vital signs closely to promptly detect such reactions as fever, dyspnea, and hypotension.
• Assess the patient every 4 hours for signs and symptoms of infection, such as fever and chills.
• Maintain strict asepsis when caring for the patient. Take measures to protect him from injury.
Being a bad host
• Watch for signs of graft-versus-host (GVH) disease, such as dermatitis, hepatitis, hemolytic anemia, and thrombocytopenia. GVH disease usually occurs during the first 90 days after the transplant and may become chronic—or it may cause transplant failure, lymphatic depletion, infection, or death.
Home care instructions
Before discharge, give the patient these instructions:
• Tell the patient to guard against infection. Warn him that he may remain unusually vulnerable to infection for up to 1 year after bone marrow transplantation.
• Urge him to keep regular medical appointments so the practitioner can monitor his progress and detect late complications.