Immunomodulators

Question 1

Define monoclonal antibodies, and describe in principle how they are made.

Answer 1

mAb = Ab derived form a single B cell

1. Immunize mouse, wait for it to make IgG and undergo affinity maturation
2. Biopsy spleen, divide Bs across wells until you have one isolate in each well
3. Fuse with multiple myeloma cell that has VDJ region KO’d –> hybridoma
4. Screen for Ab, isolate, culture 4eva

Question 2

Discuss the use of monoclonal antibodies as anti-inflammatory agents.

Answer 2

1. Make mAb Fab fragment against powerful inflammatory cytokines like TNFa or IL-1[a/B]. You can then PEGylate it to keep it in the blood stream and prevent it from crossing placenta.
2. Make Ab against human IgE, block its binding to the Fc-R

Basically, just make an Ab something that would cause inflammation and neutralize it

Question 3

Compare and contrast murine, chimeric, humanized, and human mAb. Discuss which might have disadvantages when used in human patients, and the reason for that.

Answer 3

Murine = straight up mouse Ab; good if you only wanna use it once. Otherwise, HAMA –> IC formation

Chimeric = Human C + Mouse VH/VL. Better, but still 25%(?) foreign so eventually you’ll make HACA

Humanized = Just use mouse CDR regions. Only 2% foreign, buuuuttt eventually you’ll make HAHA

Human mAb = 100% human. Take a SCID mouse and implant a human thymus, LN, and BM. Immunize the mouse, and boom - human mAbs. Make the cells hybridomas and baby you’ve got yourself a stew

Question 4

What is a NK cell?

Answer 4

• LARGE granular lymphocytes
• Part of INNATE immune system
• Kill cells like CTLs, but don’t use VDJ genes nor are they thymic-derived
• NK receptors recognize surface of “stressed” or dysregulated cells (virus, tumor)

Question 5

What is ADCC?

Answer 5

Ab-Dependent Cell-mediated Cytotoxicity

• NK can’t simply recognize ALL stressed out cells; sometimes the right marker isn’t there.
• However, it CAN bind Abs, so here’s how it works. IgG binds cell, NK binds Fc portion, NK delivers death signal –> apoptosis
• This is NOT MHC-restricted like CTL-mediated killing is

Killer-cell inhibitory receptors expressed on Natural Killer cells interact with MHC class I molecules expressed on normal cells and protect the normal cells from lysis. Cells lacking MHC class I molecules, such as some virus-infected cells and some tumors, cannot effectively engage the killer-cell inhibitory receptors and become susceptible to lysis

Question 6

Describe how a mAb against a T cell surface molecule could enhance the activity of a CTL

Answer 6

Some surface molecules, like CTLA-4 and PD-1, that, upon binding to a corresponding ligand on a target cell, send an inhibitory signal to the CTL. SOOO, if you block that signaling mechanism by covering up CTLA-4 or PD-1, the inhibitory signal can’t be transmitted and now the CTL and do its business.

Question 7

Discuss the use of modified (drugs, isotopes) monoclonal antibodies in tumor diagnosis or therapy.

Answer 7

Tag an Ab with a poison (e.g. calicheamicin, or diphtheria toxin, or a radioisotope) –> immunotoxins. They provide highly-targeted delivery of the toxic moiety.

One cool mAb can be used for imaging and a therapeutic drug, depending on which radioisotope is attached.

ALTERNALTELY, make a Fab that has two arms, one that grabs a T cell and one that grabs the tumor cell. It’s molecular glue that brings the cells together so the T cell mounts a response