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Immunological Basis of Infertility

Introduction

1. Male factor - antisperm antibody (ASA) mediated
2. Female factor - cervical mucus hostility, implantation failure, recurrent pregnancy loss
3. Maternal-fetal tolerance failure

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1. The Blood-Testis Barrier and Male Immunological Infertility

• Vasectomy (and vasectomy reversal)
• Testicular trauma or torsion
• Orchitis (mumps, other infections)
• Cryptorchidism
• Varicocele (heat-induced)
• Sexually transmitted infections / prostatitis
• Testis cancer
• Genetic associations: thymic maldevelopment, HLA-B28 haplotype

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2. Antisperm Antibodies (ASAs)

Immunoglobulin Classes Involved

• IgG and IgA are the clinically significant classes (IgM is too large to enter semen in meaningful quantities)
• ASAs may be found on sperm surfaces, in seminal plasma, and in the female serum/cervical mucus

Mechanisms of Infertility

Detection

• Direct assays (preferred - test antibodies on sperm surface):
  • Immunobead test: polyacrylamide beads coated with anti-IgG or anti-IgA; moving beads attach to coated sperm
  • Mixed Antiglobulin Reaction (MAR) test: latex beads with bridging antibody incubated with sperm
• Indirect assays: measure antibodies in seminal plasma or serum - less clinically relevant since surface binding matters most
• Threshold: WHO sets ≥50% sperm with bound beads as significant (though not firmly validated)
• Head binding is more clinically significant than tail binding

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3. Postcoital Cervical Mucus Hostility

• Antibody-coated sperm unable to penetrate mucus
• Cervical mucus antibodies acting independently

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4. Maternal-Placental Immune Tolerance

A. Trophoblast Immune Evasion

• Absent MHC class II: the trophoblast (fetal-placental interface) does not express MHC class II molecules, preventing direct T-cell recognition
• Restricted MHC class I: classical HLA-A and HLA-B are absent or minimally expressed on trophoblast, protecting it from cytotoxic T lymphocyte (CTL) attack
• HLA-G expression: a non-classical, minimally polymorphic MHC class I molecule; inhibits NK cell killing via interaction with inhibitory receptors (KIR)

B. IDO-Mediated T-Cell Suppression

• The enzyme indoleamine 2,3-dioxygenase (IDO) is highly expressed at the maternal-fetal interface
• IDO depletes tryptophan - an amino acid essential for T-cell activation
• T cells starved of tryptophan become anergic
• Experimental IDO inhibition with 1-methyltryptophan in mice causes rapid rejection of allogeneic fetuses

C. Cytokine Balance - Th1/Th2 Shift

• Normal pregnancy favors a Th2 cytokine profile (IL-4, IL-6, IL-10) - promoting antibody production and suppressing cell-mediated cytotoxicity
• Both the uterine epithelium and trophoblast secrete TGF-β and IL-10, suppressing effector T-cell development
• Th1 dominance (IFN-γ, IL-2, TNF-α) is associated with miscarriage and implantation failure

D. Regulatory T Cells (Tregs)

• Treg (CD4+CD25+FoxP3+) cells are expanded during pregnancy
• They actively suppress anti-fetal immune responses
• Treg deficiency in mice causes fetal resorption (equivalent to spontaneous abortion)
• A FoxP3-regulatory element found only in placental mammals suggests Tregs may have co-evolved with placental reproduction

E. Decidual NK Cells (uNK)

• Uterine NK cells (CD56bright) in the decidua differ from peripheral NK cells
• They facilitate trophoblast invasion and spiral artery remodeling rather than killing
• HLA-G on trophoblast interacts with inhibitory KIR receptors on uNK cells, preventing cytolysis

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5. Autoimmune Causes of Infertility

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6. Th1/Th2 Paradigm in Reproductive Failure

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7. Treatment Implications

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Summary

1. The blood-testis barrier maintains sperm as immunologically hidden antigens - its disruption triggers ASA formation
2. ASAs impair sperm motility, cervical penetration, and fertilization
3. The trophoblast evades maternal rejection through HLA-G expression, IDO-mediated tryptophan depletion, and Treg expansion
4. A shift from Th2 to Th1 cytokine dominance promotes embryo rejection and recurrent pregnancy loss
5. Autoimmune conditions (APS, oophoritis, endometriosis) are important secondary causes

• Campbell-Walsh-Wein Urology, pp. 1902-1910; 2261-2263
• Berek & Novak's Gynecology, pp. 2030-2032
• Janeway's Immunobiology 10e, pp. 759-760
• Creasy & Resnik's Maternal-Fetal Medicine, pp. 185-186

Recent evidence note: A 2025 systematic review (PMID: 40770285, BMC Immunol) confirms that ductal obstruction, orchitis, testicular trauma, vasectomy, cryptorchidism, varicocele, and testis cancer remain the principal risk factors for ASA production in infertile males, consistent with the blood-testis barrier disruption model described above.

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Antiepileptic Drugs (AEDs) in Pregnancy

Indications, Dosage & Side Effects

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Why AEDs Cannot Be Stopped in Pregnancy

• Generalized tonic-clonic seizures cause fetal hypoxia and acidosis
• Fetal heart rate slows for up to 20 minutes after maternal convulsion (fetal asphyxia)
• Risk of blunt trauma to fetus and placenta
• Children of mothers who have ≥5 generalized convulsive seizures during pregnancy have lower verbal IQ scores
• A child of an epileptic mother who convulses during gestation is twice as likely to develop epilepsy

The consensus is that maternal seizures are more dangerous than AED teratogenicity. AEDs should not be discontinued or arbitrarily reduced during pregnancy.

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General Principles of AED Use in Pregnancy

1. Use monotherapy at the lowest effective dose - polypharmacy raises major malformation rates from ~3-5% (monotherapy) to 8.6% (two or more AEDs)
2. Folic acid 4-5 mg/day preconceptionally and throughout first trimester for all women on AEDs
3. Monitor drug levels monthly - pregnancy increases clearance of most AEDs (especially lamotrigine, levetiracetam, phenytoin, oxcarbazepine); doses must be escalated
4. Target "pre-pregnancy reference level" when adjusting doses during pregnancy
5. Vitamin K supplementation in the third trimester (especially with enzyme-inducing AEDs - phenytoin, phenobarbital, carbamazepine) to prevent neonatal coagulopathy

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Drug-by-Drug: Indications, Dosage & Side Effects

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1. Lamotrigine (Lamictal)

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2. Levetiracetam (Keppra)

Harrison's 2025: "For those with epilepsy planning pregnancy, lamotrigine and levetiracetam are first-line monotherapies due to the abundance of safety data."

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3. Valproate / Valproic Acid (Depakote, Epilim)

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4. Carbamazepine (Tegretol)

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5. Phenytoin / Fosphenytoin

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6. Phenobarbital / Primidone

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7. Oxcarbazepine (Trileptal)

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8. Topiramate (Topamax)

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Summary Table: MCM Rates by AED

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Management of Status Epilepticus in Pregnancy

1. First line: IV lorazepam (preferred) or IV diazepam, or IM midazolam
2. Second line (if benzodiazepine fails): IV levetiracetam, IV fosphenytoin, or IV valproate - all roughly equivalent in efficacy (~50% success rate)
3. Refractory status: Anesthetic doses of IV phenobarbital, propofol, or pentobarbital

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Key Antenatal Monitoring Points

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Recent Evidence Alerts

• 2024 AAN/AES/SMFM Practice Guideline (PMID 38748979): Reaffirms lamotrigine and levetiracetam as preferred agents; valproate remains highest risk for both teratogenesis and neurodevelopmental outcomes
• 2024 NEJM study (PMID 38507750): Topiramate and valproate both associated with significantly increased autism spectrum disorder risk; lamotrigine was not
• 2024 Nature Communications (PMID 39548057): Large cohort confirms differential neurodevelopmental outcomes by AED class; valproate carries highest burden

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• Harrison's Principles of Internal Medicine 22E (2025), p. 3946
• Adams and Victor's Principles of Neurology, 12th ed., pp. 356-357
• Bradley & Daroff's Neurology in Clinical Practice, pp. 2907-2910 (including Table 112.4)
• Creasy & Resnik's Maternal-Fetal Medicine, pp. 1659-1660
• Katzung's Basic & Clinical Pharmacology, 16th ed., p. 677