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Immune System and Infection

Comprehensive overview of innate and adaptive immunity defending against infections, mechanisms of immune dysfunction (primary/secondary immunodeficiency), opportunistic infections in immunocompromised hosts, and immunomodulation strategies (vaccines, immunoglobulins, biologics).

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Internal Medicine department. Book Appointment →

What is Immune System and Infection?

The immune system is a complex network defending against pathogens through two arms: innate immunity (rapid, non-specific, includes physical barriers, neutrophils, macrophages, NK cells, complement) and adaptive immunity (slower, specific, antigen-specific memory). B cells produce antibodies (humoral immunity); T cells coordinate cellular immunity (CD4+ helper, CD8+ cytotoxic, regulatory T cells). Cytokines, chemokines, and pattern recognition receptors (TLR, NLR) orchestrate responses.

Immunodeficiency states predispose to infection: primary immunodeficiencies (SCID, CGD, common variable immunodeficiency) often present in childhood with recurrent infections; secondary immunodeficiencies result from HIV/AIDS, malnutrition, malignancy, immunosuppressive therapy (corticosteroids, biologics, chemotherapy), splenectomy, and aging. Specific deficiencies predispose to characteristic infections: humoral defects → encapsulated bacteria; T-cell defects → opportunistic intracellular pathogens; neutrophil defects → bacterial and fungal abscesses.

Management strategies include infection prevention through vaccines (live vaccines contraindicated in severe immunocompromise), antimicrobial prophylaxis (TMP-SMX for PJP in HIV, CMV prophylaxis post-transplant), immunoglobulin replacement (IVIG/SCIG for antibody deficiency), and immunomodulation (G-CSF for neutropenia, biologics for autoimmune disease). Aggressive treatment of infections in immunocompromised hosts is essential due to atypical presentations and rapid progression.

Symptoms

Recurrent severe bacterial infections (sinopulmonary, skin)
Opportunistic infections (PJP, CMV, candidiasis, aspergillosis)
Chronic diarrhea or failure to thrive (in children)
Persistent or unusual fevers without clear source
Severe or atypical viral infections
Disseminated infection from typically localized pathogen
Poor wound healing and abscess formation

Risk Factors

HIV infection (especially with low CD4 count)
Solid organ or hematopoietic stem cell transplantation
Hematologic malignancies and chemotherapy
Long-term corticosteroid use (>20 mg prednisone >2 weeks)
Biologic therapy (TNF inhibitors, JAK inhibitors, B-cell depletion)
Primary immunodeficiency (genetic disorders)
Asplenia or splenic dysfunction (sickle cell, post-splenectomy)

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Recurrent infections (>4 ear infections, >2 pneumonias, >2 sinus infections per year)
  • Failure to gain weight or grow normally (child)
  • Persistent fevers without identified source
  • Severe or unusual infections
  • Poor response to standard antibiotic therapy
  • Family history of primary immunodeficiency
  • Symptoms developing during immunosuppressive therapy

Treatment Methods

01
Antimicrobial prophylaxis tailored to specific defect
02
Pneumocystis prophylaxis (TMP-SMX) for HIV CD4 <200, transplant patients
03
Vaccination (avoiding live vaccines in severe immunocompromise)
04
Immunoglobulin replacement (IVIG/SCIG) for humoral deficiency
05
Aggressive treatment of breakthrough infections with broad-spectrum antimicrobials
06
Hematopoietic stem cell transplantation for severe primary immunodeficiency
07
Immune reconstitution therapy and cytokine support (G-CSF for neutropenia)

Which Department to Visit?

You can visit our Enfeksiyon Hastalıkları department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

Learn About Enfeksiyon Hastalıkları Department

Let us help you

You can make an appointment with our specialists or contact us for your concerns.

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Hepatitis A (HAV)

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Hepatitis A is an acute, self-limited liver infection transmitted via the fecal-oral route causing acute hepatitis without chronicity; supportive care suffices in most cases, while vaccination prevents outbreaks and post-exposure prophylaxis within 2 weeks is effective.

Hepatitis B

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HIV/AIDS Information

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.