Reactive Lymph & Infectious Mono

Lymphocytes Lineage

1. Stem cells (HSCs)

2. Common lymphoid progenitors

3. Lymphoblasts

4. Prolymphocytes

   1. Mature B Lymphs

      • Memory B Cells

      • Plasma cell (effector cells

   2. Mature T Lymphs

      • Helper T cells (HTLs)

      • Cytotoxic T cells (CTLs)

   3. NK cells (Precursor is common lymphoid progenitors)

Reactive Lymph Characteristics

• Pleomorphic (broad range of sizes & shapes)

• Lower N:C ratio, dark blue rims, skirting of RBCs

• Reactive lymphocytes seen in the blood smear is activated cytotoxic T (CTL) not infectious B lymphocytes

• Historically classifies as Downey cells

Lymphoblast

• High N:C ratio

• Fine chromatin, prominent nucleoli

• Scant basophilic cytoplasm (little cytoplasm, dark blue rims)

Prolymphocyte

• More cytoplasm than lymphoblast, chromatin more condensed

• Prominent nucleolus

Infectious Mononucleosis

• Caused by Epstein Barr’s Virus

• Symptoms include fever, sore throat, splenectomy, posterior cervical lymphadenopathy (enlarged lymph at the back of neck)

• Clinically associates with reactive lymphocytes, and leukocytosis

• Infected B lymphocytes produce heterophile antibodies of type IgM (NOT specific to EBV) that can be tested with Mono-Latex.

Sue-Vue Color Mono Test {Principle, SOP}

• Reagent containing animal RBC that have specific antigens induce response to heterophile antibody

• NOT specific to EBV, only support but does not confirm diagnosis

SOP

• 3 circles for positive, negative controls, and patient sample

• Add 1 drop of controls or patient sample to the corresponding zones

• Add 1 drop of color reagent to all tests, mix and spread (AVOID cross-contamination)

• Rock side-to-side for 2 minutes

• Positive test shows agglutination and heterophile antibodies are detected. Next step is to consider EBV-specific serology

Plasmodium vs Babesia {Transmission, Life Cycle, Diagnosis}

Plasmodium

• Transmitted by Anopheles mosquitoes, common in endemic subtropical regions (Africa, Central & South America, Southeast Asia)

• Life cycle involves liver and blood stages

Babesia

• Transmitted by Ixodes ticks, common in northeastern U.S

• No liver involvement

Malaria {Pathology}

• Caused intra/extravascular hemolysis that leads to normochromic-normocytic. Leukopenia & thrombocytopenia

• Diagnose with thick & thin smears

4 species (most common → least)

• P. vivax: Schüffner’s dots, amoeboid-shape trophozoite, visible schizont

• P. falciparum: banana-shaped gametocyte, no schizont or trophozoite, multiple rings per RBC

• P. ovale: Schüffner’s dots and enlarged RBC

• P. malariae: Schüffner’s dots, band-shape trophozoites

Babesia Life Cycle

Human/Animals (asexual)

• Tick introduces Babesia sporozoites into the bloodstream

• Sporozoites entered RBC and develop into trophozoites

• Asexual multiplication

• Ruptured RBCs that caused hemolytic anemia and released merozoites that infect more RBCs

• Differentiates into male/female gametes

Ticks (sexual)

• Gametes fuse and sexual reproduction

P. Falciparum vs Babesia

Percent Parasitemia {SOP, Formula}

• Count between 500(high parasitemia >10%) or 2000 RBC (low parasitemia < 1%)

• Use two counters to track infected RBC and total RBC

• $$\%\text{parasitemia}=\frac{\text{infected}}{\text{total RBC}}\cdot100$$

Malaria Life Cycle

1. Mosquito injects sporozoites into bloodstream

2. Sporozoites enter liver cells and develop to merozoites (daughter parasite produced by multiplication process)

3. Liver cells ruptured, merozoites released and infected RBC

4. Enter RBCs and metabolically develop in the trophozoite stage, undergoes multiplication in the Schizont stage

5. RBCs ruptured, merozoites released to infect more RBC

6. Some merozoites produce gametocytes instead