EXHIBIT 10.115

May 15, 2002

Wayne Tyo

Re:      Revised Terms of Retention Bonus/Severance Offer

Dear Wayne:

         Nexell Therapeutics, Inc.'s Board of Directors has authorized me to
extend the following offer to you to remain with the Company through September
30, 2002, or the wind up of its operations, which ever is earlier. The effective
date of the wind up of the Company's operations will be determined by the
Company in its sole discretion.

         1. Duties and Responsibilities

         You will be responsible for financial analysis, reporting, cash
management and other duties or responsibilities assigned by me or the Board or
other governing body from time to time. After the Company vacates the premises
at 9 Parker in Irvine, you will be asked to work out of your home. The Company
will reimburse you for reasonable out-of-pocket expenses associated with
operating a home office upon receipt of appropriate documentation. You will be
allowed to use certain office equipment of the Company in your home office and
may keep this office equipment provided you do not voluntarily resign before
September 30, 2002.

         2. Compensation and Benefits

         Your salary will be continued at its current level through September
30, 2002. If the Company involuntarily terminates your employment before
September 30, 2002, you will be paid the salary you would have earned through
September 30, 2002 as a lump sum, less applicable withholdings. If you
voluntarily terminate your employment before September 30, 2002, you only will
be paid your salary earned through your last day of work and will not receive
any salary from the day after your last day of work through September 30, 2002.

         Your group health insurance benefits will be maintained at their
current level through September 30, 2002. If your employment terminates
involuntarily before that date, you will be paid a lump sum equal to the cost of
the applicable premium that you would have to pay to continue your coverage
under the Company's group health insurance plan through September 30, 2002. This
benefit is separate and distinct from the COBRA contribution benefit described
in Section 3 below. If you voluntarily terminate your employment before
September 30, 2002, your group health insurance benefits will terminate in
accordance with applicable plans and COBRA.




         3. Severance Benefits Offer

         Effective May 15, 2002, your entitlement to the severance benefits
listed in this section 3 (collectively "Severance Benefits") became vested,
subject to any conditions set forth in this letter:

            a. You will receive a severance payment equivalent to eight (8)
               weeks' base compensation, in the gross amount of $________, less
               applicable withholdings.

            b. You will receive a COBRA contribution benefit in the amount of
               $_______, which is equivalent to the current cost of three
               months' premiums paid by the Company for the Company-sponsored
               group medical and dental insurance benefits currently provided to
               you and your dependents.

            c. The Company will provide professional outplacement services, as
               defined and selected by the Company, for a period of up to three
               (3) months following your termination of employment. You may
               elect to receive a lump sum payment in lieu of receiving the
               professional outplacement services.

         The Severance Benefits are payable following the termination of your
employment for any reason, whether voluntary or involuntary, provided the
Company receives the original of the Employment Termination and General Release
Agreement ("Release Agreement") signed by you and the seven (7)-day revocation
period provided for in the Release Agreement has passed. This Release Agreement
may not be signed by you before your last day of employment with the Company. A
copy of the Release Agreement you will be required to sign as a condition of
receiving these Severance Benefits is attached as Exhibit A to this Agreement.

         You acknowledge and agree that the Retention and Severance Plan for
Senior Staff Members will be terminated effective May 16, 2002, and you will not
be entitled to any benefits under this plan.

         4. Additional Retention Bonus

         If you remain employed until September 30, 2002, or your employment is
involuntarily terminated before September 30, 2002, you will receive a one-time
retention bonus equal to eight (8) weeks' base compensation in the gross amount
of $___________, less applicable withholdings. Payment will be made as soon as
possible following September 30, 2002 or the involuntary termination of your
employment, whichever is earlier. You will forfeit the right to a retention
bonus if you voluntarily terminate your employment before September 30, 2002.

         5. At-Will Employment/Entire Agreement

         This letter constitutes the entire agreement between you and the
Company regarding the subject matter herein and supersedes all prior and
contemporaneous negotiations, understandings,





or agreements, whether oral or written, expressed or implied. The severance
benefit offer and retention bonus programs described above do not change the
at-will nature of employment at Nexell. Employment with Nexell is at-will,
meaning that it may be terminated by Nexell or you for any reason or for no
reason, with or without notice, and with or without cause. Only the President of
Nexell has authority to enter into an agreement contrary to this policy of
at-will employment, and any such agreement must be in writing and signed by both
you and the President of Nexell to be effective.

         You acknowledge and agree that you have been given a reasonable
opportunity to review this letter. You understand that you may obtain
independent legal advice from your own attorney, and have done so to the extent
you so desire before signing this letter. You are not personally relying on any
agreements, promises, statements or representations made by the Company or its
attorneys, except as expressly set forth in this letter.

         Your contribution and efforts are greatly appreciated. Please sign this
offer letter where indicated below and return the original to me.

Sincerely,



William A. Albright, Jr.
Chief Executive Officer and President

ACCEPTED AND AGREED:

____________________________
Wayne Tyo

____________________________
Date